"About MacBook Pro Retina SMC Update v1.1 (504KB)
This update resolves a rare issue where users may experience slow frame rates when playing graphics-intensive games on the 15-inch MacBook Pro with Retina Display. It also includes bug fixes for Power Nap, fan speed control and wake from sleep.

After this update has successfully completed, your SMC Version will be: v2.3f35

System Requirements: OS X 10.7.5 or later, OS X 10.8.2 or later"

The 10.8.3 update is recommended for all OS X Mountain Lion users and includes features and fixes that improve the stability, compatibility, and security of your Mac, including the following:

(list of fixes later expanded)
• Ability to redeem iTunes gift cards in Mac App Store using your Mac's built-in camera
• Boot Camp support for installing Windows 8
• Boot Camp support for Macs with a 3TB hard drive
• Fix for an issue that could cause a file URL to quit apps unexpectedly
• Fix for an issue that may cause Logic Pro to become unresponsive with certain plug-ins
• Fix for an issue that may cause audio to stutter on 2011 iMacs
• Fix for an issue that may cause the screen to display incorrectly after waking from sleep
• Fix for an issue in Messages that may cause messages to appear out of order after waking from sleep
• Fix for an issue that may cause the desktop picture to change after logging out or restarting
• Improves compatibility with IMAP servers in the Notes app
• Allows the Slideshow screen saver to display photos located in a subfolder
• Fix for an issue in Contacts that may cause cards to print out of order
• Fix for an issue in Contacts that may cause addresses to print in the wrong location
• Reliability improvements when using a Microsoft Exchange account in Mail
• A fix for an issue that could cause link aggregation to not complete after a restart
• A fix for an issue that could cause delays when logging into an Active Directory account on high latency networks
• Xsan reliability improvements
• Fix for an issue that could cause Active Directory accounts to be locked out after accessing the Security & Privacy pane in System Preferences
• Includes Safari 6.0.3

(See doc below for security fixes)

Here are OS X 10.8.3 articles on changes/security fixes and delta/Combo Update download pages.

Related Docs
• About the OS X Mountain Lion v10.8.3 Update
• About the security content of Safari 6.0.3
• About the security content of OS X v10.8.3 and Security Update 2013-001
  
  Download pages
• OS X Mountain Lion Update v10.8.3
• OS X Mountain Lion Update v10.8.3 (Combo)

OS X 10.8.3 release build is 12D78. See today's new/updated Apple articles list below for more 10.8.3 related docs and downloads of new Boot Camp software updates.

You can check Apple's OS X Mountain Lion Forum for feedback/any common problems reported. For mac model specific issues/fixes, check the forum for your model. Saw a post in the mac mini forum (in previous thread) noting improved display color/contrast after the OS X 10.8.3 update and the long MacBook Pro thread on WiFi issues had some posts it was not fixed in OS X 10.8.3. There's also reports of better PC nvidia card support/improved drivers.
(BTW: On a Late 2012 Mac Mini (2.3GHz Core i7/16GB ram/Intel 520 SSD) I saw a surprising increase in Cinebench OpenGL scores with OS X 10.8.3 - 26.51 vs 22.85 with OS X 10.8.2.)

FYI/Warning for Intel X25 SSD Users:
There's several reports from Intel X25 SSD users that it requires the latest firmware to be compatible with OS X 10.8.3. Otherwise it will not boot on a restart after the update. (Here's the download page for Intel's SSD firmware update tool.)
BTW: No problems updating to OS X 10.8.3 in a Late 2012 Mini w/Intel 520 series SSD boot drive. (And a nice OpenGL CB score boost as noted above.)

(Some widespread apple acct/mail problems Thursday, not OS ver specific. See earlier post.)
  

"About Security Update 2013-001 (Snow Leopard)
Security Update 2013-001 is recommended for all users and improves the security of OS X.
For information on the security content of this update, please visit this website:https://support.apple.com/kb/HT1222
(here's the specific doc on security fixes in the update)

SHA1= dc52d0f7d2db6080c57c7b9252a4d85c5e178450

System Requirements: Mac OS X 10.6.8"

Here's Download pages for Client and Server:
• Security Update 2013-001 (Snow Leopard)
• Security Update 2013-001 Server (Snow Leopard)
• Security Update 2013-001 (Lion)
• Security Update 2013-001 Server (Lion)

Not sure it's common but after this update (10.6.8) had a reader say his apple ID/.me email PW failed. Ditto when booting to an OS 10.5.8 boot drive, so must be something on apple's end. (Hopefully just temporary.)
FYI: Apple's services system status showed all OK (green) but there's a note about some users of iCloud services affected today:

"Account and Sign In - 4:52 PM - 6:02 PM (EDT) - Some users affected
Users may have incorrectly received an authentication error when attempting to use iCloud. Setting up a new iCloud account from an eligible device may have been temporarily unavailable. "

Errors/failures reported here also affected OS X mail, not just iCloud/new acct usage. (mail in 10.6.8 working again as of Fri AM.)
  

• About the OS X Mountain Lion v10.8.3 Update
• About the security content of OS X v10.8.3 and Security Update 2013-001
  (Includes fix for Java Web start working even if plugin disabled in OS X Lion/Mountain Lion)
• About the security content of Safari 6.0.3
• OS X Mountain Lion: Supported digital camera RAW formats
• OS X: Login window partially appears, cursor redraws screen (said fixed w/10.8.3)
• EFI and SMC firmware updates for Intel-based Macs (added rMBP update 1.1)
  
  Apple Boot Camp 5 and Boot Camp 4.x Software Update Downloads:
  (each linked page includes info on supported macs and windows versions)
  
  • Boot Camp Support Software 5.0.5033
  • Boot Camp Support Software 4.1.4586
  • Boot Camp Support Software 4.0.4326
  • Boot Camp Support Software 4.0.4255
  • Boot Camp Support Software 4.0.4131
  • Boot Camp Support Software 4.0.4033

  For feedback on Boot Camp/driver updates, check Apple's Boot Camp forum.
  
  

• Boot Camp 5: Frequently asked questions
• Boot Camp: Installing Windows 7 Frequently Asked Questions
• Boot Camp: Frequently asked questions about installing Windows 8
• Boot Camp: Thunderbolt devices not recognized after Windows 8 upgrade
• Boot Camp: About keyboards and key assignment for Microsoft Windows
• Boot Camp: System requirements for Microsoft Windows operating systems
• Boot Camp: Windows installation boots to black screen with blinking cursor
  
  
• iMac (27in, Late 2012): Boot Camp alert with 3TB hard drive (said fixed in OS X 10.8.3)
• iMac: "Windows 8 not supported on this Mac" alert message (said fixed in OS X 10.8.3)
• Windows 8, iMac (Mid 2011): Keyboard screen brightness controls do not work
• MacBook Pro (13" Late 2012): Distorted or black screen during Windows 8 install
• MacBook Air (Mid 2012): "Free up space on Drive C" alert during Win 8 upgrade
• Win 8/Boot Camp 5: MacBook Air (Mid 2012) won't start or displays low res graphics
• Windows 8: "Uninstall USB 3.0 eXtensible Host Controller Driver" alert when upgrading from Windows 7
  
  
• Using USB 3 devices on Mac computers FAQ
• AirPort and Bluetooth: Potential sources of interference
• iMac (Late 2012): VESA mount compatibility
• About the SD and SDXC card slot
• iPhone, iPad, iPod: TV out support
  
  
• iOS: Connecting to the Internet
• iOS: How to transfer or sync content to your computer
• iOS: Transferring information from your current iPhone, iPad, or iPod touch to a new device
  
  
• Understanding your support coverage and service options
• Can I get phone support if my product is outside of coverage?
• Important documents to keep after buying an Apple product
  
  
• How can I learn if I'm eligible to purchase an AppleCare agreement?
• How to manage your AppleCare agreements
• Do I need to register my AppleCare agreement?
• How to transfer coverage of an AppleCare agreement
• How to request a refund for an AppleCare agreement
• How to view or print Proof of Coverage for your AppleCare Agreement
• How to register an AppleCare agreement for an out-of-warranty product
• Do I need to register Apple accessories with my AppleCare Protection Plan?
• How to update proof-of-purchase information

• Apple store has iMacs with Built-in VESA Mount Adapter (in 2011 $40 extra)
• 2012 Mac Mini user's Tip for Dell 2413 Display problem
• LightWave 3D Group unveils Architectural Design Bundle
• Apple and Facebook Flash Forward to Computer Memory of the Future (wired)
• Apple eyes wireless charging via the iPad Smart Cover (cnet)
• Jobs to be manga hero in Japanese comic series (pocket-lint)