Had my MacBook Pro for about 4 months now and finally decided to max out my HDD since I was cutting it close with the stock 250GB. The Seagate Momentus seemed like the obvious choice as it is on of very few 7200RPM drives and there was a lot of good review on it so I decided to go for it. After an easy installation I went with a clean install rather than image the stock HDD and restore it. The speed was easily noticeable. An erase and install on the stock HDD took around 20 minutes while on the Seagate Momentus it only took 15 min. Start up times also decreased as did the launch of applications (tested on CS4 and only took 10 seconds to open compared to the 20 seconds+ with the stock HDD) so based on that, there is a definite speed increase. The big question to everyone looking into getting a Seagate Momentus is how is the vibration and how is the sound? For sound, it's not that bad and is on par with the the stock 5400 HDD but might be a bit louder (fans) depending on your tolerance. For the vibration, again based on tolerance it might differ from user to user, it is easily noticeable and is like a constant "humming" or "buzzing". Pretty significant if you use it on a hard surface, you can feel that surface vibrating as well. I read a few other reviews and those users said that it's not noticeable if you use the screws and bracket. I checked those out and everything seems to be screwed it tightly and snugged but the vibration is still there. Overall, the speed increase is there and will definitely help with load times of the OS and large applications. But the vibration would be the biggest draw back of the Seagate Momentus. If you're still undecided on which 500GB HDD you should get for your MacBook (Pro), I would recommend looking into a Western Digital 500GB 5400 HDD. Based on reviews, the performance is on par with the Seagate Momentus without the vibration. Should be noted that if you press down on the right palm rest, the vibration does seem to go away which could suggest that if there was someway to add something in the HDD bay it could reduce the vibration significantly. EDIT: I tried to see if I could lessen the vibration with rubber, corks but nothing seems to work. I'm going to see if I can call the store tomorrow and ask if I can get an exchange for another unit or get a WD Blue. I know I won't be able to get used to it with the constant "humming" sound due to vibration.