I have right now 2 WDC's in the RMA package and ready to go to post office to send them (older WDC 40GB AB-5400rpm but still under warranty, and new WDC 80GB 80JB -7200rpm -SE edition). I realized that all WDC are prone to bearing whine sooner or later, and I'm finished with WD brand unless they'll upgrade their bearing technology.
Btw, I always used to buy WDC drives (and thought that the whine is inevitable) until I bought some IBM's, Maxtors and Seagates in the last 1-2 years .... I see that bearing whine is really a WDC "specialty", and the only good thing about WDC is that they seem to replace their whiners without further questioning. When they are new and quiet they work very nice, but they won't stay quiet often too long. Others may think otherwise, but this is my experience. I currently own some 8-10 WDC's.
dave
I forgot to mention one maybe somehow important fact; all my boxes are very quiet - I use either quiet, quality low-rpm fans (thermal controlled, variable speed & plain low rpm), or undervolting other fans (incl. CPU fans) if necessary and when possible to bring the noise down. In this environment I can clearly hear if drive emits noise or not.... for instance the Enermax fans in my HDD cages spin somewhere around 1500 rpm...