Virtualization in CentOS 5.2

[networkengineer]

I was wondering if anyone has had any experience with the Xen environment that CentOS boasts vs some other form of virtualization server such as VMware or Virtual Iron..

Mainly to answer:
Stability running windows server 2k3?
Failover capability? Any tutorials? (if one VM fails, can it be mapped to another such in VMware?)
Clustering VM?
Desktop Virtualization Support?

Read quite a bit in the generalizations about it, but would like to hear from someone who has done it and I'd like to hear the takeaways.

Thank you in advance!