This is something that I was able to help test for a little bit. The idea behind these drivers is to make certain devices in a fully virtualized guest “xen aware”. Since the heaviest used parts of a hosted operating system are networking and disk access, they focused on improving them. For right now the supported operating systems are RHEL 4 and 5, and windows 2000, 2003, and XP. Without sounding like a sales person, I thought this was a really cool idea. Those that have run fully virtualized guests, you can understand why this would be welcome. Anyways, here is a link that you can read.