If you're after something to use as an all encompassing media server and don't mind spending more money then ReadyNAS, ReadyNAS, ReadyNAS.
Hmm. That's quite a bit more money. We're into "why not just use a normal PC?" territory.
Basically, I'm looking for always-available NAS, with the ability to do snapshot backup to an external disk periodically. The ability to snapshot my laptop (and Jenni's laptop) would be good too, but I've got her fairly well-trained to save important stuff to the shared drive.
I figured that since the WD ran Linux (although it's only got 32MB RAM, so couldn't run my web server, unfortunately), it'd be fairly hackable to do what I need.
I'd prefer something silent, with low power consumption. Then I could run my web server on something mini-ITX-ish, and turn off my Windows server when I'm not using it.