I also have a sheeva plug as my server, but if i did it over I would choose to grab an mac mini. My big jump to the sheeva was the power usage, but then I found out the mini only uses 12W! Along with the 12W you get a x86, with hd, cd drive, wifi, etc on a box that I can easily load linux (upgrading the sheeva's kernel isn't the easiest...) and in a few years when done with it I can easily sell the mini unlike the sheeva.
None of these have over 350W PSU's, and I don't think any of these rigs will draw anywhere close to that power. All I have is anecdotal evidence that my electric bill has increased by maybe $14-$20 a year. Running my stereo for a day probably eats more power than these things take all year. Plus, my livingroom in my apartment stays nice and warm during the midwest winters. I'm pretty happy with spaceheaters with processing power :)
edit: the real issue is that I can't get a cable connection in my neighborhood with higher than .7mbit up, so it's not like I 'm serving loads of content. I use these for running different tasks usually. Two are dedicated DB servers and the other 3 run whatever projects I'm consulting on this/ that week.
I use a VIA x86 system for my server.
18W peak from the wall, no fan (which is one less moving part to fail). Since it replaced an old P4 system (200W from the wall), I shaved $30/month off my electric bill
It seems like ARM servers are the best choice for home servers. They have adequate processing power and are cheap.