Early releases of the Xen hypervisor showed promise but had lots of rough edges. Citrix's XenServer 5, however, is very much a production-class virtualisation solution with features that match, and in some cases exceed, what's available on rival...
Native support for DAS/NAS/SAN storage systems ; Offloading of common storage processing tasks ; Automated provisioning and resource balancing ; Live migration and other high availability options ; Bundled management console and P2V converter
XenCenter console is complicated in places ; Advanced high availability and dynamic provisioning features are absent from the Standard Edition