Well we have run FOG on xen (it is not the Citix xenserver product) for years. Currently on 1.2 but just today made a copy of the VM to upgrade to 1.3 (We need Vista and to a lesser degree XP). We use it to process old PCs going out the door, DBAN wipe, Bios updates, asset tag removal, and imaging with the OEM OS. We have probably processed over 5,000 PCs (and some Macs, different story) over the years.
Do you have specific questions or just researching?