Just got a macbookpro 13" (unibody). I swapped out for the Seagate 7200.4, nearly stripping a screw in the process... checked with apple store geniuses, screw is still fine. .it's my crappy screwdriver. Getting a decent 00 screwdriver shortly. Don't forget to have a good Torx T6 handy. Thanks to the apple store genius, who also reseated my hard drive.
Initially I thought it had a lot more vibration, so much that I had a new drive shipped to me today (which I will try soon). I have the first 7200.4 although the vibration seems slightly less after the genius touched it. 😉
What I noticed... if I put my rest my hand lightly on the right-side palm-rest. I definitely feel the vibration (not too annoying), but very noticeable. I also noticed that my desk is also not flat, so that rubber foot (on the bottom of the laptop) is not touching the desk. When I put both hands on the laptop to start typing, the vibration drops off to nearly nothing. I am still suspicious, because I thought it was running hot (and there was strange discolorations on the circuit board underneath the drive.. like corrosion). To be fair, it was getting hot during the OSX re-install and the bootcamp install. 😛