Some people here are using a 3D Windows application named Rhinoceros. I set up a Windows 7 virtual desktop on RHEV 3.1 and showed it to one of the users. He said that Rhinoceros was laggy but that it performed about as well as some of older physical computers in his lab. He was excited at the prospect of making it available to users on a virtual desktop.
One issue is that the Num Lock key didn't work on the Windows remote-viewer. It seems to work on Fedora 18, however. Hopefully, this will be fixed in RHEV 3.2.