Out of the 11x 2TB drives I have in a system, I'm pretty sure 8/9 of them are the WD Green.
I've left the power saving things on them, so in terms of speed, you lose a lot there waiting for spin ups. Over the network they provide enough to give peak windows to windows of 90m, then drop to.. 60/70 ish. Windows to Lion I don't know cos there's no speed thing. On the same computer, transfer speeds are as-good as I've seen.
The non Green ones I got are the WD Black, and have a few green/black as spares.
I did get a bad batch of WD Green at one point, but that happens with everything you buy. I buy WD out of personal preference.