Most of my VMs are Linux servers, but the few Windows servers (including 2008 R2) that we run seemed fine on the automated tools upgrade. The only one giving me trouble is a Linux server that accidentally had a Xen kernel, so it fails the checks during the tools install with an ironic message about needing to be real hardware, or a VM or something. I forget... but it gave me a chuckle after I realized the cause of the issue.
I was actually impressed with how well the automated tools upgrades worked. Enough so that I shift-clicked whole sets of servers and let it do its thing in batches. No disasters.
At this point, I'd say the overall system is running better than any previous edition we've had with the exception of the inane ctrl-key bug for remote console control from OS X webkit-based browsers (basically, I can't send so much as a cntrl-c - a very hobbling problem in the unix world - to a VM using anything but Firefox).
- Aaron