Out of the blue, Microsoft has released beta 1 of their virtualization hypervisor Hyper-V (formerly known as Viridian). Microsoft seems to have got working on this much quicker than what was anticipated earlier.
It seems the annoucement went live on the 13th, but I didn't see any mention of it until just now. Interesting to see that Quick Migration, as opposed to Live Migration, is still on the table. All in all, the feature set still reads as Microsoft is still playing catch-up with VMware and that there probably won't be any big surprises for the final version scheduled for release 180 days after Server 2008 goes RTM.
For the full details and specific release information, check the Microsoft Press Release and the Hyper-V site.