I connected two mac pros via fw800 and used target disk utility. I later restarted one mac and forgot to unplug the fw800 cable. Later, I saw the slaved mac in the 'shared' column on finder. Activated screen share, controlled as normal - and then realized that the mac wasn't connected via airport or ethernet. I was controlling it just from the fw800 cable and hadn't set anything up.
The new mac pros are fantastic. I'd never seen this happen before, but it was awesome. Add that to the super ease of adding more RAM (64 gigs!), and how completely easy they make it for you to add a blu ray drive from OWC - this is certainly my favorite mac pro iteration yet.