Good but interestingly vacuous
One of the great attractions of Xen or KVM is that it allows you to isolate those Windows servers you'd rather not be running into well-contained little virtual machines so you don't have to spend hours (days? weeks? months?) trawling the net for barely functioning device drivers from the different hardware vendors -- one, simple, small hardware environment and that's yer lot.
Meanwhile, of course, those antique legacy windows apps that you have to keep those Windows servers around for can just sit there in their little virtual machines and you don't need to worry about non-existant hardware upgrades or anything like that.
The same can be said, to a large extent, about old Linux distros running in virtual machines.
What's interestingly vacuous though is Red Hat's lack of clarity on the hypervisor: Xen, KVM or both? Xen would appear to have a place in the data centre whereas KVM would appear to have its home on the desktop (at the moment) -- but the choice of tested Windows variants would tend to guide one towards Xen.