i bought a WD Scorpio Black 750GB. i installed it in my optical bay (i have a silent SSD in my main bay) and immediately noticed how loud the drive was. i exchanged it for another one thinking that the drive was somehow bad, and the replacement is just as loud, and i mean annoying loud. i also noticed my battery drains very fast now.
in my previous macbook pro, i had a 750GB Seagate 7200 RPM in the optical bay, and i couldn't hear that drive at all, it was dead silent. the Scorpio Black sounds like the macbook pro fans, but its not the fans, its the hard drive. i love the speed of the drive, and i really like the 5 year warranty, but the noise is just too much. i'm just not sure i want to keep the drive.
i've read of other people claiming that their WD Scorpio Black 750GB drives are very quiet. they must be in a somewhat noisy environment cause, for me, two in a row have been very noisy. i can hear the drive as i write this post, and its annoying the heck out me