Until yesterday, I was quite happy with their cool and quiet operation. And then I found this thread. It's from the Linux Kernel Mailing List; you can find many archived versions by searching for "Western Digital GreenPower drives and Linux".
The gist is that the read/write head on these drives parks itself too often. While this does result in power savings while parked, the drives are only designed to support 300k parks (consumer drives) or 600k parks (enterprise/RE2 edition).
I don't know if this problem exists on Windows or not. I would assume it does, at least under some scenarios.
On Linux, I use a program called smartctl to read SMART data from the drive. This program is also available on Windows (but I'd wager there are also GUI-based tools that do the same).
Either way, the smart data will show how many times the head has been parked via the "Load_Cycle_Count" parameter.
An (edited) example from one of my drives:
smartctl -a /dev/sda Power_On_Hours 3377 Load_Cycle_Count 97972
That averages out to 29 loads/hour... every two minutes!
The "solution" so far has been to use the "wdidle3.exe" DOS utility provided by Western Digital to change the head-park idle timer to a different value (or disable it all together). I just found out about this issue yesterday, so I haven't had a chance to actually do try this yet. I found this FTP site that has a copy of the wdidle3.exe program.
Anyway, if anyone else has any info on this issue, I'm eager to hear it.