We're running U1 w/ I forget what misc. patches, I need to look. It's been stable for us so far, backups - and restores - seem to be working fine. We're due for another round of patching to satisfy some requirements, I just really don't want to break it.
I have the impression U2 broke some stuff (CBT again?) so I'm very leery of applying it and risking our backups. Hardware version on VM's runs the gamut of I think 8 up to 11. Tools is 10.0.0.9 on at least most if not all but I've recently setup a Baseline to get those squared away.