As I mentioned in my previous post...I have a rack of servers sitting in a spare bedroom - 6 in fact (keyboard tray, SATA storage array and all!). It's been a long time in the making, but I have a PowerEdge 6650 I'm dumping stuff on to - primarily some social websites I run and development playgrounds. I have to say - overall...I'm pretty darned pleased.
Right now I'm running Virtual Server 2005 R2, primarily due to some major headaches I had getting VMWare up and running...particularly when I found out that the current version of VMWare Server can't run VMWare Workstation 6 machines - whoops (as in - a weekend blown kind of whoops). That's a bit of a gotcha to me.
That being said, I'll likely be moving back to VMWare once the new version of server is up...there are a ton of extra features it has...and the general consensus is that performance is better on VMWare (helllooooo gigabit ethernet!).
Either way - at the moment, I'm happy that my power bill will at least drop a little bit for the time being, but I imagine it'll take another weekend once VMWare Server is out to get things in order again...
FYI...a pretty decent comparison on the two - a bit dated, but ...
http://www.windowsitpro.com/Windows/Articles/ArticleID/45253/pg/2/2.html