I've built a dual 64-FX system. It screams along quite nicely I might add.
I've drooled over it several nites after it was up and running. (I know I know... but that's just me)
If you like linux, and you've been waiting forever for 64-bit arch like I have, then this is definately the thing for you.
However, prices are still a little steep. I had to spring for it because I needed the 64-bit system for my development.
The Ultimate Linux Box was a good article. But I didn't go with their specific hardware. You can actually get the sata working, but it's really tricky. At least it was for me 'cuz I hadn't worked with sata and linux before.