"I've got a 15" MacBookPro 3,1 ("Late 2007") model (running Mac OS 10.4.11). The new drive is a Seagate Momentus 7200.4 (ST9500420AS) 500GB. This is the model with 7200 rpm and without "G-Force protection". The height is 9.5 mm (12.5 mm wouldn't fit in the 15" MBP) (Of the Pre-Unibody MBP's, only the 17in model can take 12.5mm high drives. All Unibody's can though.) and the cache size is 16MB. The drive firmware version is 0002SDM1.
I've read quite a lot about Mac and PC users having problems with clicking sounds and apparently too many HD load cycles due to head parking (here for example www.xlr8yourmac.com/feedback/OS_X_notebook_HD_cycling.html) (Article here from early Feb. 2009 on the subject. Not specific to OS X, the page just has reader/OS X user feedback.)
I didn't see that before so I thought I'd ask Western Digital's and Seagate's support, because I was undecided anyway, between the WD Scorpio Blue 640GB (5400RPM) and the Seagate Momentus. After seven days, I still haven't got an answer from Western Digital. But through the live chat function on Seagate's website, within 10 minutes I was told that all Segate HDs, with or without G-force protection, sold after August 2009, would work fine.
Also the friendly live chat person at OWC told me their WD drives would work ok but they'd sell the Seagate drive only without G-Force Protection. (FYI - Dec. 9th news page here had reader feedback on WD Scorpio 750GB and 640GB HDs) So I thought, buying the Momentus without the -G suffix would be the safest bet.
(For owners of HDs with builtin Shock Sensor, you can disable Apple's SMS (sudden motion sensor) from the terminal - sudo pmset -a sms 0.)

Here are some bench test results of the drive as startvolume, with 100GB used on the drive after cloning the old system to the new drive using "Carbon Copy Cloner". (Disk Utility's Restore tab can also be used to clone drives, although it has no option to omit specific files/folders, etc.)
Xbench Version 1.3
System Version 10.4.11 (8S2167)
Physical RAM 4096 MB
Model MacBookPro3,1
Drive Type ST9500420AS

Disk Test (overall) Score: 42.97
Sequential Score: 60.31
Uncached Write Score: 26.42 / Detail: 16.22 MB/sec [4K blocks]
Uncached Write Score: 159.94 / Detail: 90.49 MB/sec [256K blocks]
Uncached Read Score: 59.96 / Detail: 17.55 MB/sec [4K blocks]
Uncached Read Score: 180.02 / Detail: 90.48 MB/sec [256K blocks]
Random Score: 33.37
Uncached Write Score: 10.48 / Detail: 1.11 MB/sec [4K blocks]
Uncached Write Score: 175.49 / Detail: 56.18 MB/sec [256K blocks]
Uncached Read Score: 83.63 / Detail: 0.59 MB/sec [4K blocks]
Uncached Read Score: 146.41 / Detail: 27.17 MB/sec [256K blocks]

The "AJA system test" (that can be downloaded here: www.aja.com/products/software) ranged between 90 and 95 MB/s read and write performance in it's default setting.

The temperature (measured with "Temperature Monitor") did not get hotter than 45°C and got down to around 35°C within a few minutes (at 19°C room temperature). This was the same with the old drive. But I think it can get hotter during summer, for example.

The old drive was a Seagate Momentus 7200.2 (160 GB, 8MB cache, 7200 rpm), original Apple bto option. I did some tests with the hd before exchanging it.
For the old drive the AJA score was only around 50 MB/s (about half the speed of the new one), much like it's results in Xbench. I remembered it to be a bit faster so I checked the disk fragmentation in "ShowVolumeFragmentation" (it runs in Rosetta I think).
Much to my surprise, even though there was over 30GB free space, the fragmentation of the free space was to 41% "orange" (not good). I think that despite what you expect from OS X, the disk really can get fragmented in two years. This has an impact on performance, I'm sure.

I have put the old drive in a USB case. Usually, you can't retrieve any SMART info from the drive over a USB or Firewire connection. But this case from "RaidSonic" has a special SMART feature to submit certain info from the drive to a dedicated Dashboard Widget: www.raidsonic.de/en/pages/products/external_cases.php?we_objectID=5557
What's primarily shown is the temperature and the "power on-off circles" (Cycles?) of the drive (whatever that means exactly). The widget also has a user-definable alert function if the drive gets too hot. In my tests (copying and simultaneously duplicating large files for 30 minutes), the hd did not get hotter than 43°C. The widget however, shows the "highest ever reached temperature" of the drive as 56°C. (IIRC most notebook drives are rated for up to 60°C.)

The noise level of the new hd is more or less like the old one. The new hd may be a little louder (that means it is clearly audible), but still ok for me. There are no unusual clicking sounds. The clicks that the drive makes are relatively quiet anyway.
I can't feel any vibration from the drive. I have used the drive for a few hours in an external case and there was a minor vibration, but that seems to be damped by the MBP case now. For sensitive persons, the noise is more a factor, I'd say.
All in all, I am very happy so far with the decision for this hard drive.
Best regards, Wolfgang"