I bought the 40 GB drive from buy.com last week during free shipping days to support the in-state retailer. Unfortunately, it broke down so I'm RMA'ing it. While the drive didn't completely die, for whatever reason, a day after installation it was operating at 1/30 of full speed. When it was initially working, it was fast and whisper-quiet. The reviews I've read seem to indicate that the new WD 40 GB is faster, but generally a little pricier.
To make a long story short, I still have faith in this particular drive so I ordered it this afternoon from Outpost.com. It has already shipped and is due for delivery tomorrow. I'd suggest taking advantage of Outpost's free shipping/no sales tax policy, even though they price the drive a few dollars higher. Yes, they are a retailer participating in Quantum's rebate program.