hey, i have an aluminum macbook unibody (A1278). just upgraded from the 320gb hdd from apple to a new 500gb seagate one. did everything according to the ifixit guide here, http://www.ifixit.com/Item/500_GB_7200_RPM_Seagate_SATA_Hard_Drive_%28New%29.
i can tell you it is loud as $^^* and i'm a little annoyed. by comparison the 320 was barely noticeable. the new drive takes longer to spin up and spin down, too, so putting it to sleep isn't quite as snappy as it was. PLUS if i hold the laptop at an angle, the hdd whines... the old drive never did this. i can only conclude that 7200 isn't suited to laptops. maybe i should have researched that first. anyway, i'm looking for ways to minimize it and next time, i'll probably go straight to SSD.