Not too worried about performance right now. It'll essentially be a NAS over 1Gbit/s, so as long as it's faster than that.

I was planning to build a file server using OpenSolaris in the coming weeks, but I may have to rethink that now.

Anyone know a good place to get access to ZFS in another place? Would BSD or FUSE on Linux be better?

It's more general purpose, and you can make your own UIs for it. I'm in the middle of doing one myself.

Where's BOINC? BOINC may not have as many users or processing power, but it is more diversified than Folding@home.

I don't know if I'd go as far as to say Linux will crush Windows 7 (it seems to be quite good actually), but I do believe Linux will continue creeping up in the OS share. I own three computers: a Mac running OS X Leopard, and two PCs, both of which dual-boot Linux and Windows. I've found that quite a few configuration things require diving into the command line, which is often beyond what most people expect. Example: to turn off tap-to-click on my laptop (annoying as hell!), I had to edit X's configuration file, then restart X. Restarting X isn't a problem (log out and in will do the trick), but editing a configuration file? I bet most would be scared shitless of screwing it up.