I've been using Proxmox since 1.8 now 2.3 for a couple years. It runs my Win SBS 2003, WHS 2011 vm's great.
Linux and Win run almost bare metal speed for me with default settings. Not a single hitch with speed or reliability. I use IDE mostly to keep it simple. I've heard good things about using virtio disk/net with win but I haven't got around to trying them. IDE/E1000 works well so I figured why bother.
The proxmox wiki can be a bit sparse and high tech level at times I have to admit. That's been my only complaint.
I have also run Xenserver with Win servers in CloudStack 3/4. That works well too along with XenCenter for mgmt. Might give that a try. Its also free.