What is the pro shooting with?
If this is going to be long term working relationship, it might be best to get something that uses the same lens mount (unless he's shooting with an Hassy or something to that fact). If the the pro is shooting with a 5D, you should seriously consider an XTI. If the pro is shooting with a D3 perhaps a D40 etc.. That way you can borrow his/her lenses as well. Your camera also serves as a backup AND the workflow will be the same.
I met a professional portrait wedding photographer who basically a one man show. He does frequently hire assistants when necessary but requires them to use the same camera as he shoots.. even if it means lending them equipment. All for the same reasons.
As you can tell from my response, i really recommend an SLR of some sort. If you must have a P&S, pretty much the Canon powershot G series is about the only camera I can recommend without any second thoughts. Very near SLR quality, uses the same flash packs as Canon's DSLRs, and wonderful IQ. A G5 is my current knock around P&S but I am impressed by the G6 and the G9. The G7 was missing RAW which was a deal breaker for me. The G7 and G9 both missing the swing out LCD display. The G9 did not feel nearly as comfortable in my hands as the G6 nor the G5. The G9 had faster shutter response than both the G5 and the G6.