I just replaced a 5400 rpm 320 Gb Western Digital (not the stock drive) with a Momentus XT in my late 2007 MBP, and I couldn't be more impressed. The eternal beach balls are gone. Granted, I've never had an SSD, but the speed boost from this thing is unbelievable. I didn't even do a clean install, just a restore from Time Machine. I didn't do formal benchmarks, but I did time my boot sequence before and after: Old Drive Chime to Login Screen: 46 seconds Chime to launch Safari and open web page: 2:58 Momentus XT Chime to Login Screen: 22 seconds Chime to launch Safari and open web page: 38 seconds So, the new drive can boot and open a web page faster than the old drive could get to the login screen. Altogether 2 minutes and 20 seconds faster. Not that I reboot very often, but it gives you some idea of how much faster everything is. I was so fed up with how slow my MBP was that I almost bought a new MBP for $2000, then I almost bought a 200 Gb SSD that wouldn't have had enough space for $340 (would have had to also buy an optibay and worry about losing hibernation or shock protection). So glad I just spent $130 and got a huge performance boost for very little money or hassle.