XenServer 6.0 was released in late September, 2011. I am currently working on building out my test cluster, as I expect to role out our first XenServer Server (hey that's redundant) in the next few weeks. I expect to be posting a lot more on the subject as I become more familiar with the product.
Release notes below.. includes new features:
Xenserver 6.0 Administrators Guide below for those of you who can read.