I spent some time this weekend playing with the MSDN virtual labs, and it worked remarkably well, it was a far better and more enjoyable experience than I had expected. The whole process went very smoothly, and my only problem was some delayed rendering of the remote machine, thanks to my very slow net connection. It does look like a very cool example of Virtual Server automation.
Mostly, I played with the BizTalk labs: the 2006 Business Rules Engine one and the 2004 BAM one. It would be nice if they finally got the BizTalk 2006 BAM hands on lab up, since it is far nicer than the 2004 one.