Gartner just released an updated Magic Quadrant for x86 Virtualization, and I am happy to read (as I am Oracle Employee) that Oracle is on the way up :-) Sure VMware is still leading the pack, followed by Microsoft, but Gartner is seeing customers more often evaluating alternatives to prevent lock-in with VMware.

According to Gartner: “There has been growing interest during the past year in competitive evaluations and creating a separate virtualization footprint with a different technology — typically Microsoft Hyper-V, although Oracle VM use is also growing among VMware customers.”

x86 Virtualization Magic Quadrant

See the full Gartner report, it is an interesting and fair analysis of the current x86 Virtualization Market.
The Gartner Magic Quadrant report