VirtualBox 4.1.8: (released 12/19/2011) - See the Change Log for list of chgs/fixes.
I welcome feedback on v4 - including from those that had problems with previous versions and users of commercial products like Parallels or Fusion.

Reader Reports: (later reports first)
If you've used VirtualBox, please send your feedback on your experiences (pros/cons, etc.). Please include the VBox version you're using as well as Mac Model/OS X version, Windows or other OS version it's running, etc. (And especially interested in any specific features/reasons why you'd buy Fusion or Parallels instead of using VirtualBox - some older VBox reports below have noted issues with networking in VB for instance.)

VirtualBox v4.1.6 on OS X Lion, running OS X 10.6.x in VM:

(added 11/28/2011)
"Virtual Box 4.1.6 on Lion running Snow Leopard in VM
Snow Leopard works OK in Virtual Box 4.1.6 with some minor oddities such as "About this Mac" not being available. The VM merely restarts. There may be other oddities but I am not aware of them.

Figured out how to get USB stick recognized without Guest Additions as Additions cannot be installed for the Mac OS.

• Before starting SL in the VM go to VM Settings/Port, insert desired USB stick in rear USB port on MacBook Pro (I think this maybe the same USB bus the the keyboard uses), and click the + sign on the right so that the USB stick is listed, unplug the USB stick.
  
  
• Start the SL VM and after the desktop comes up, insert the USB stick in the rear usb port. If you get a small white button with an orange dot in it in the USB icon at the bottom right hand corner of the Virtual Box window it will mount.
  
  
• If it does not mount click the USB icon in the Virtual Box Window to see that the USB stick is checked and the name of the stick is NOT grayed out. If it is grayed out remove the usb stick, quit SL and Start the SL VM again. Try again to see if the USB stick is recognized.

To get a screen resolution other than the default use the information provided for Method 1 in this link. PCWiz Computer - [Mac OSx86] How To Change Resolution (VMware) I tried the second Method altering the .plist but could not get it to work. Method 1 has to be entered at the boot prompt at every launch.
(FYI: See report below on changing rez per info in VBox user manual section 3.12.1
Wil later wrote so far he's not been able to get that to work.)

I used Snow Leopard in VirtualBox to run Quicken 2006 rather than run between computers. I wish Intuit/Quicken would come up with a release that has the attributes of Quicken 2006 that will run in Lion. Quicken Essentials is nice but does not have the reports showing both income and expense (debit and credits) in one report that can list up to a full year in a single window.
I currently run Windows Quicken 2009 in CrossOver (wine) but continue to keep Quicken 2006 going in the hopes that soon Intuit will release an acceptable version of Quicken for Lion.
Regards, Wil N."

Another VBox user mail today with info on changing resolution in VM:

(added 11/28/2011)
"I am running VirtualBox 4.1.6 (virtualized 10.6.8) on my Mac Pro (host 10.6.8). I was able to change the virtualized screen resolution by following the instructions in the user's manual section 3.12.1, "Video modes in EFI". For example, by typing in the command "VBoxManage setextradata "VM name" VBoxInternal2/EfiGopMode 4" in the host Mac OS terminal application, the next time I booted I had a virtual screen resolution of 1440x900. This setting persists until changed.

Besides having to use a USB drive (as mentioned in report above) to transfer files between host and virtualized machines, this runs pretty well for my limited needs (primarily Canvas) once I upgrade to Lion.
-Ted M."

Virtualbox 4.1 running under OS X Lion w/2011 Mac:

(added 8/01/2011)
"After picking up a new Macbook Air 13" 1.8 GHz Core i7, 4GB/256GB earlier this week, I got around to setting up a a new WinXP VM in VirtualBox 4.1.
Fresh XP installation was fast (from .iso on the SSD), applying the last two years of updates and installing the few programs I need was quite fast and painless.

My 2.4 GHz 15" Santa Rosa MBP (6GB/500GB) always chokes the system when doing heavy disk I/O in the (Parallels) virtual machine. My new air easily multitasked during the XP install/updates/application installs -- I'm very impressed with the SSD.
~ashes"

(added 7/29/2011)
"I have a 2011 MacBook Pro 13" 2.3Ghz i5 with 8GB memory (320 GB HDD) running 10.6.8 and (in a separate test partition) Lion 10.7. I have a need to run WinXP for configuring network devices and telephone systems, and have used (prior to the 2011 MBP 13) VM Ware, but decided to go with VirtualBox (which I have used for quite some time on my desktop system for software testing) instead of upgrading VM Ware.

I have been running VirtualBox 4.0 since purchasing the MacBook Pro 13in in March under 10.6 and have tested VB 4.0 under Lion with no issues. This morning I upgraded both the Snow Leopard and Lion versions to VB 4.1 with no issues.

VirtualBox on the 2011 MacBook Pro 13in has been a very good performer (actually faster than native Windows XP on my wife's 3 year old ThinkPad).
I would not hesitate to recommend VirtualBox running on a 2011 MacBook Pro 13" laptop.
-Fred K."

(added 7/29/2011)
"I have been using VirtualBox 4.1 on a mid 2011 MacBook Air 13in 1.8Ghz i7. I copied the VMs from a Windows machine and for the past week I have not had any issue with any of the VMs I have (Win7, Win2003-64bit, OpenSuse). And I do database design and Business Intelligence work on the VMs daily.

The only thing that may come up is the fan getting really loud when I started Oracle on one of the VMs. SQL Server does not seem to cause that.
Hope that will be useful to you and let me know of you have any questions or something I can test for you.
-Serigne"

(Older reports on VirtualBox follow)

(added 12/29/2010)
"Upgraded my long trusted Win XP from VirtualBox 3.xx to V4.0

Fixed it with the suggested package from download site...
Works like a charm, but I do still miss the "drag and drop" copy option of files, that both VM Ware Fusion and Parallels have!

I have heard that VirtualBox is slower then the others, but I never noticed that.... I am not a heavy app user, just do some online stuff which macosx wont let me.
The new version seems much less CPU intensive - my cpu temp is 59C, earlier I had temps around 65C.
Nice update!
-MacDoktor"

(added 12/27/2010)
"VirtualBox 4.0 is a big improvement! The extra's pack provides USB 2.0 support and provides for automatic recognition with just a simple one click to add any device in the USB Settings folder.
Version 4.0 has improved the installation of Guest Additions in Linux without the need to use the Terminal.
I mainly use VBox as a hobby, trying various OS's. I have used Parallel's through 4.0 (not v5 or v6) and while it has some enhancements over VirtualBox, VirtualBox is free and is sufficient for my purposes.
Regards, Wil N."

VirtualBox 3.x Feedback:

(added Sept. 25th, 2009)
"I've got 3.0.6 installed on my (2009) Nehalem Mac Pro, and I have been unable to install CentOS 5.3 (64-bit) so far. It gets through all the initial install steps, then hangs at random places during the actual install. I'm installing from an ISO image, the same one I used to do VMWare installs.

It's odd, I can't seem to determine a pattern for the failure, it's always at a different point in the install.

(Just for the record I asked what OS X version he's running and if he'd reported the problem to VBox's developers)
10.5.8. I've had issues with 10.6 on my Pro at home, so I've decreed a very slow rollout at work. (Never mind that a number of the special-purpose apps. we use don't support it yet.)

Not yet (reported this to VBox). I'm just getting started with VB. I've done a good amount with VMs, going back to SunPC 1.0 in 1990 or so, and lots of different stuff since on both UNIX and MacOS/OS X with and without coprocessors. I did the early betas of both Parallels and Fusion, and am pretty much a Fusion user now, tho on UNIX I use Xen for hosting.

In the case of Virtual Box, I got interested when Sun bought it (I worked for Sun years ago), and decided the other day to try it in our work environment. If I can ever get CentOS loaded, I want to go head-to-head with Fusion on the same machine - maybe Parallels as well, though in my mind the latter is only really good at Windows.

I'll look up the feedback info today if I get a chance and drop them full details, I'm happy to help out. Virtualization has always appealed to me.
-Pete W."

If anyone has a suggestion/tip (or sees the same problem) send a note.

(added Sept. 24th, 2009)
"Reinstalled VirtualBox 3.0.6 on MacBook2,1 (late 2006), 1.83GHz, 4GB ram running OS X 10.6.1 and 128GB Crucial SSD (Firmware 1571). Tried to reinstall Parallels 4.0 upgrade but it does not recognize previously 3.0 upgrade code and 2.5 full install code. Checked their web site for additional info but was following correct procedures.
Actually, after install Windows XP SP2 and observing performance I see no reason to go back to Parallels. I do have Windows on Boot Camp but performance increases with SSD now seem to make the Boot Camp partition unnecessary for my needs.
Regards, Wil N."

For me personally, the only reason I boot to Windows (bootcamp/separate HD install) is for 3D/gaming - and even a fast drive wouldn't make VM a good choice for that.

(added Sept. 21st, 2009)
"Setup: VirtualBox 3.0.6 installed on an iMac 2.4 GHz (2007 model, 4GB RAM) under 10.6.1 and 10.5.8 (the former on the internal drive, the latter on an external FireWire drive).
No problems here with various flavors of Linuxen (Ubuntu, CentOS, Fedora). VMs are generally set up with 1GB RAM and single processor.

1. In response to Lawrence B. (ref: earlier report below) and adding the Guest Additions to Fedora:
In a fresh, standard installation of Fedora 11, the guest additions require the installation of the compiler and kernel headers, like so (in a Terminal window, with the guest additions CD mounted using the menu item):
(The part starting with "#" are comments and don't need to be typed in.)

su - root
yum install dkms # install this package per VirtualBox instructions
yum install gcc # guest additions need compiler and kernel headers
cd /media/VBOXADDITIONS_3.0.6_52128
sh ./VBoxLinuxAdditions-x86.run # or -amd64.run for 64-bit installations
shutdown -r now # restart to activate guest additions

At least in my 64-bit virtual machine, this enabled the guest additions.

2. In response to Peter G. (earlier post below) and networking virtual machines:
The network adapter is set to NAT by default, so VirtualBox acts like a router and hides all virtual machines from the surrounding network, including the host machine. By changing the network adapter to a bridged adapter, the networking interface of the virtual machine uses the host's networking interface and talks to that network directly, e.g. it will contact that network's DHCP server for an address. In Peter's home network, the virtual machine would now get an address in the 192.168.0.x range, and other machines on that network could now access the virtual machine and any services running on it. (This may be easier than setting up port forwarding on VirtualBox.)

Chapter 6 in the user manual describes virtual networking in more detail.
Hope this helps,
Tilmann"

(added Sept. 21st, 2009)
"The one feature I want to use that VB doesn't support is running Mac OS X Server in a VB window. It would be nice to be able to test on 3 or 4 different MOSX server versions in place of having to BUY dedicated hardware to do this and still have to re-install constantly.
I've used both parallels and fusion to do this in the past.
-troy"

(added Sept. 18th, 2009)
"Re: VirtualBox 3.0.6
I too installed VirtualBox on my MacBook Pro 13" (4GB RAM, 500 GB Seagate drive from OWC). Windows XP Pro installed fine. I tried to clone a FreeBSD 6.2 server I have, and the level 0 dumps worked fine for the "/" "/tmp" and "/var" partitions, but every time I tried to restore the dump onto the virtualbox machine for "/usr", the OS would fault and the virtualbox would restart. Haven't had time to figure out what is wrong yet.

I'm using a command similar to the following:
ssh BoxWithBackupsOn cat /path/to/backup | zcat | restore -rf -

Anyway, life with Windows XP on virtualbox is pretty good,
Life with FreeBSD is providing a somewhat rocky start.

I have had no issues with the network connection running XP or FreeBSD.
It's a little weird because I'm on a 192.168.0.x network at home, so VB esentially creates a sub-network in the 10.0.0.x range. So it's a 10. routed to a 192.168. routed to the internet. I haven't tried attempting to use the VB client OS as a server and trying to access it from a different machine on my network.
-Peter G."

(added Sept. 14th, 2009, updated Sept. 21st for SL 64Bit Kernel Note)
"Re: VirtualBox 3.0.6
Mac Pro Early 2009 (4,1), 2.66 GHz, Quad Core with 4GB RAM
Using VirtualBox 3.0.4 and now 3.0.6
All device volumes on secondary drive
App running from primary/boot drive

Successfully booting and running:
Windows XP Pro
Fedora
Ubuntu
Xubuntu
DSL

Have been unable to add "VB Guest Additions" to Fedora device, all others OK. (Update/FYI - see reader's tips above) Able to run full screen or windowed. Boot times are fast and performance is stable.
For all setups I have granted 1024 MB of RAM and 128 MB of VRAM.
Have had 3 VirtualBox's running simultaneously with minimal impact on MacPro performance.

(What OS X version is the Mac Pro using? (10.5.x or 10.6.1)-Mike)
OS X 10.6.1 currently, initial set up was under 10.5.8.

(I asked if he had seen any problems using his internet connection in VM/Windows (which some VB 2.x users had reported earlier).)
I have noticed no internet problems so far - browsing is quick, automatically downloading and installing MS updates as scheduled.
My first version was 3.0.4, upgraded to 3.0.6 with SL - I was experiencing the password/authentication prompts reported by others.
(I was curious if VB had 64bit kernel support.-Mike)
Have not tried it yet - but if I do I will update. I have found that 64 bit breaks my current version of Cisco VPN - so for now staying on 32 bit.
(Update - he later wrote)
Ran VirtualBox in 64 bit. Image attached shows 64 bit VB?
-Lawrence B."
(screenshot from Activity Monitor, scaled/cropped to save space here)

VirtualBox 2.2.4 Feedback:

(added June 2, 2009)
"Quick note on VBox (2.2.4) on a 2007 MacBook Pro - this still does not support the internal microphone in Win XP guests. I actually am pretty impressed with VB, but I have to run VoIP apps under Windows and don't have an amplified external mic or USB mic, so no VBox for me.
The internal mic works fine in either Parallels or Fusion.
This deficiency has also been present for at least two years, so I would assume it will never be implemented.
-fb"

FYI - Reports below were using VirtualBox versions 2.2.2 or earlier

(added May 8, 2009)
"I have used VirtualBox and have been pleased. I have previously used Parallels v1, 2, 3 and VMware Fusion 1 and 2.
I primarily use VirtualBox for MS Access at work. The speed is nice and comparable to VMware Fusion 2. The feature I like the best is the ability to PXE boot. I haven't had success trying that with Parallels or VMware Fusion.

I work for a liberal arts college and we do all of our Windows imaging through Zenworks via PXE boot. When people first started switching from Windows to Mac at work they would use Bootcamp. Some to run Windows for certain applications they didn't want to replace due to price, others just to have a security blanket in case they couldn't figure out how to do something form OS X. (the main reason I run windows is gaming, and use bootcamp/Native boot for max performance in 3D games.)
Just like everyone else, they would tire of rebooting for one or two apps. So we started deploying Parallels. Both Parallels and Bootcamp required I recreate our Windows images from scratch. Eventually VMWare Fusion came out around the same timeframe as Parallels 3 was out and we were having tons of speed, USB, and stability issues with Parallels. So we switched to VMWare Fusion. For Fusion users I would use Vmware Workstation for Windows (free) to PXE boot and create a Windows VM with our Windows image. I would then copy that VM from the Windows machine to a Mac and open with Fusion and install VMWare tools. This worked pretty well with good speed and stability.
I was happy with this when I read a press release on Sun Virtual Box. The only reason I gave it a shot is that it claimed to support PXE booting on the Mac. I had low expectations being a free product but it has worked well. I now can bring a Windows image down to a Virtual Box VM on the Mac via PXE which saves me a lot of time and trouble deploying Windows on Macs.
I hope this helps.
Thanks, Mike F."

(added May 8, 2009)
"I used to use Virtual Box for a Windows 2003 (Ser ver?-Mike) environment which I use to develop on Visual Studio 2005. I had to move to Parallels as I found an issue with Virtual box.
I VPN to my office via a PPTP connection. I use the Bridged Networking as the NAT won't allow me to connect to the VPN server (Multiple layers of NAT) However, Since I am hosting this all on my Macbook it is going across my Airport card to my Airport Extreme. When I connect to the VPN after a short while the airport card will stop working and I need to reconnect to the AP. (What version of VirtualBox were you using? (latest is 2.2.2, released last week IIRC)-Mike)
Parallels works no problem with bridged Networking.
I do continue to use Virtual Box for Linux guests though as Parallels tools for Linux suck and have not been updated to work with the latest ubuntu.
(he later wrote)
It is Windows Server 2003 Enterprise. I use it as the application I do development on uses an SQL 2005 Database. It is just a pain to set that up in XP and Server 2003 performs very well in a Virtual machine as it doesn't have all the gui stuff that XP has.
So I started with Virtual Box 1.4 and the issue was still in the last update before 2.2.2. I love Virtualbox but since I need to be connected to the VPN 100% of the time so I have access to our Repository at the office, it was a show stopper. I continue to use virtualbox for Linux guests and the latest version now supports compviz in ubuntu so I get all the cool eye candy ;)
Best regards,
The Main Family"

If anyone else has seen this problem with VirtualBox or has a suggestion, let me know.
(I share internet access using an 802.11N Airport Extreme base bridged to a DSL modem with both Macs and PCs - although I use bootcamp/native Windows, not a VM.)

(May 7, 2009)
"I use VirtualBox at work extensively. It pretty much has feature parity with Parallels and is free. It offers the same Windowing modes including coherence (where the start menu and Windows Apps integrate into the UI with Mac apps).
Things like shared folders are almost as easy as with Parallels, which has a slight edge since it installs a driver that sets up the Mac as it's own Workgroup that's visible only to the virtualized PC. Unless I'm mistaken, Virtual Box lacks user folder sharing (very handy for having iTunes on both and using the same exact Library) as well.
Overall, If I didn't already own a copy of Parallels I would be using Virtualbox at home as well.
-Max"

(May 7, 2009)
"After a debacle trying to upgrade from Parallels 3 to v4, I deleted them all and started over with VirtualBox.
It is free, of course, so my expectations were lowered some. But it does pretty much all parallels does, and not so invasive with your system. Just installed the new Win7RC, it works well.
You'd be hard-pressed to come up with a reason not to use it! :)
Best, Gunnar"

I noticed PCworld has a short article today on Windows 7RC1 on a Macbook Air using VirtualBox.a

(May 7, 2009)
"VirtualBox is great. I've used it for testing Linux, Solaris and other OS configurations. The best part is the FREE part. Hopefully the Sun/Oracle deal won't destroy VirtualBox and it's FREEness.
-Rob D."

(May 7, 2009)
" In addition to Parallels I have used VirtualBox and find it to be a very good VM machine. My main use was for the Linux distribution Ubuntu. It is rather "geeky" in that you must learn to use some command line stuff like changing directories such as cd /cdrom to access "additions" for installing additional functions. There is a lot of support stuff out in the "cloud" via "googling" or "yahooing" some of which is quite detailed and some rather simple even on the same subject. I tend to use the simpler methods due to my limited linux command line capabilities. The best part is that it is free and very stable.
Regards, Wil N."

I welcome other user feedback on VirtualBox. (Especially any specific features/reasons why you'd buy Fusion or Parallels instead.)