Mike Garcen at the excellent Home Theater PC News Site, MissingRemote.com has a great comparison of Windows Home Server systems. He compares a home brew "frankenstein" build with a Antec P180B chassis vs. a custom built Windows Home Server housed in a Chenbro ES34069 and finally a HP MediaSmart Server EX475. A great five-page write-up worth a read for anyone considering Windows Home Server.
Many SageTV users are using Windows Home Server as their operating system since SageTV is the only HTPC software to support it. You read right, Microsoft still doesn't support WHS in Vista Media Center - it doesn't make sense, but it's true.
Check out the Battle of the Windows Home Server Systems at MissingRemote.com