I'm using Win 8 in a home built headless server running Windows Home Server in a VM. It works really well as I'm able to run the Win 8 server as a media server (recording FIOS and serving it to around the network) and as a backup to all my PCs. Win 8 is much more flexible than Win 7 for my needs. Yes, I ignore the Metro interface.
You make it, we break it.