Today Terry Wilcox, my grad students working on virtualization informed me that he had Xen installed and working on our virtualization testbed (two dell 6650's with 4 CPUs and 16Gb of RAM). Working means that he can transfer running instances from one box to the other. We have been doing a lot of performance studies of VMWare's ESX, but switched to Xen for the next part of Terry's research.
The reason isn't that we wanted some infrastructural diversity, although that's not all bad. The reason is that we had reason to fear that VMWare might hinder the publication of Terry's work, a risk we can't afford to take. They'd sent us a (nice) email about some earlier work we'd published informing us that our license doesn't allow us to publish performance information. So, we'll route around the issue entirely and use Xen.