The reason a lot of stores like BestBuy and CompUSA and the like list only "PC compatibility" is because those drives they sell come with formatting/diagnostic utilities on either a CD or a floppy that work only with Windows PCs. They don't come with Macintosh formatting/diagnostic utilities.
The drive will work in your machine, as the others have said here. I have four Western Digital drives in my G4 tower and they work flawlessly. I've even got a 10GB and a 20GB that have been in there since 1999 and they're still humming along today, and I leave my computer on 24/7.
Yes, the 7200RPM Western Digital drives I have are a bit noisy. They "whine" a lot. Not distracting, but you won't have a silent computing experience with them. Doesn't matter a whole lot to me since I can't hear that well to begin with, but it may bother those who are seeking silence.