I am working with a company that wants to perform a greenfield install of 6.5 and consolidate their 5.5 environments. The manager is pretty adamant, however, about leaving the VM Hardware versions alone "in case something goes wrong" and they have to port back to the 5.5 instance. I am looking for decent documentation on any issues with running old VM Hardware on 6.5, as they have 4, 7, 8 and 10 presently, but haven't come across anything.
Has anyone run into any KBs or any personal experience doing things this way? I see from the compatibility list that these versions are all still supported, so aside from simply adding work of having to again shut down 1000 servers to do the hardware upgrade down the road, are there any potential issues?