Yes, its interesting but you need to read the small print. You get the
hypervisor  and what else? What can you really do with it?

 See this discussion in the Technet forum.

http://forums.technet.microsoft.com/en-US/winserverhyperv/thread/64564e20-96f2-4
949-902b-69ecec631392

I've played with both their ESX and VMWare Server (previously GSX) and find
the VMWare Server is equivalent to MS Virtual Server. The ESX server runs on
a small linux kernal and I found it harder to work with, requiring
additional 3rd party tools for me to be effective with it. I must admit I
prefer their Physical to Virtual conversion tool, it is much better then
Microsoft's current options.

We opted to go with Microsoft however, we don't like the vender finger
pointing that will eventually occur when there's a problem later on.