I've been using RH in a Win7 VMware virtual machine just fine. But I'm only using it as a slicer. Not for printing. But it should work for printing. The only potential I could see for a problem in printing would [possibly] be millisecond delays as the gcode traverses the virtualized environment and passes thru the physical hardware to the device.
I had been using an WinXP SP2 VM in the same capacity previously before I changed to a new VM.
Did you have a specific VM question?
I assume you're probably running XP as a VM within Mac?
If its going to lead off topic, lets open a new post and notif me.
SD2 w/ mods: Rumba controller, ATX PSU, SD pro case, glass bed, with more to come...