I run CQC in a VM and so far the only issues I have had were not CQC related. They mostly centered around getting COM ports and USB devices to pass through successfully to the guest. But I am running on the now deprecated VMWare Server not on an ESX host... I also use RDP as my primary means of accessing CQC through android phones/tablets and there is no issues with delay, etc (as long as you assign enough resources). But you can run the interface viewer on any windows machine, or use a RIVA client on IOS or android clients.
CQC itself is very lightweight, I originally started running it in a 512MB VM on XP. I have since bumped that up to 2GB in order to support multiple RDP sessions.
It is modular (as I think Elve was) so you can distribute the various components to run on machines near your resources, although they may need to all be in the same subnet/broadcast domain to find each other. Jonathan was a long time user and big contributor to CQC before founding Elve, so a lot of the concepts are similar. The primary fundamental difference that I see is Elve leverages .NET as something more people are comfortable with, whereas CQC tries not to be dependent on underlying libraries in an effort to maintain stability. So it's all custom windows/dialogs, macro language, etc.