When Ray Noorda ran Novell he coined the term Coopertition to describe their relationship with us. Microsoft's Kevin Turner described this as "Shake hands but keep the other hand on your wallet".
We would love customers to buy ONLY Microsoft stuff (support would be SO much simpler), and competitors would love customers only to buy their stuff. A world where we go 100% of spending of x% of the customers would be so much neater than the real world where we get x% of the spending (on average) of 100% of customers. Both we and competitors want customers to have a great experience of our respective technologies, and that doesn't happen if we don't cooperate on some things.
In the virtualization world it means two things ; being able to run competing OSes on our virtualization and being able to run our OSes on competing virtualization and give the customer clarity about support.
So first, if go to http://windowsservercatalog.com/ and click on the ‘certified servers’ link on the right side of the page under the Windows Server 2008 logo, you can check which Servers have been validated in the lab- there a sub-section for servers validated for hyper-v.
Second if you go to Server Virtualization Validation Program page and click on the 'products' link on the left side of the page you can find out which products we support. As you can see VMware is on the list their entry says which version of Windows is supported on which version of VMware. Today it's 32bit Windows 2008 only, on ESX 3.5 update 2 only. That would tend to make people nervous about older versions of Windows until you the section which appears next to each catalogue entry "Products that have passed the SVVP requirements for Windows Server 2008 are considered supported on Windows 2000 Server SP4 and Windows Server 2003 SP2 and later.". It would be reasonable expect more products from more vendors to appear on the list, but it's good to see that VMware was one of the first to pass the tests.
Third. Linux support. Mike Sterling has posted that Linux Integration Components are now posted , the actual link he provides to the connect web-site seems to be broken, but you can find the components in the Connections Directory
Steve and I are off to Edinburgh to do the 5th run of our Virtualization tech-ed event Seats are still available for tomorrow (Thursday 11th).