Back in the days I wrote a paper on how to automate Xen virtual machine deployment, one of the side advantages of abusing systemimager in this way is that you can also rebootstrap your physical machines on a virtual machine with no effort.
The only disadvantage is that you have to make a golden image of the server.
Basically the whole P2V concept is just showing how little of a typical infrastructure can be reproduced automatically (10th floor test anyone ?)
A machine should be able to be reinstalled to the last known point with no effort, physical or virtual shouldn't matter.
Apart from abusing systemimager to do the job, you really need to peak at openQRM. Matt should probably put some videos on youtube , but with openQRM you can migrate boxen from Physical to Xen, from Xen to VMWare, frmo VMWare back to Xen and so on ..
As for non unix operating systems .. frankly ..