I am running Snow Leopard Server as a guest on a Lion (in order to run a couple of old Rosetta apps -- please don't give me advice on this). Since a Mac guest on a Mac host cannot run in Coherence mode, I put the guest in Full Screen mode in it's own Desktop (AKA Spaces). However, once I do that, there is not an easy way to switch back to the host. I can use a keyboard command to get into the guest under Lion, but can not find a key command to get back out of it. Any suggestions?
I have the same problem, contacted the Parallels Support today but nobody there could help me. They say Apple set some limitations and a Keystroke command to reach the host system is not possible. I would really appreciate if somebody has a hack for this