Scott - this shows my ignorance - but figure I'll ask - when you say Xen and XenXerver have merged - do you know if this means that the snapshot mechanisms of XenServer that were missing in Xen are now in both?
Let me reword that for more clarity. The Xen and XenServer projects have merged. XenServer is now the complete "backup package" officially supplies, fully free and open source, by the Xen project itself. Xen, technically, remains the hypervisor used inside of XenServer and can still be deployed via Suse, Ubuntu, NetBSD, etc. separately.
With the change, though, we now have XenServer standing fully as a Xen official package to compete with HyperV and vSphere while Xen is a reference to the hypervisor kernel itself (like Red Hat v Linux.)
So no, the snapshot functionality remains in XenServer, not in Xen (the kernel.) But as XenServer is no longer a competitor to Xen, the overall effect is that Xen matters little as a stand alone concept today and XenServer is really the unified target for end users and backup vendors.