SHO-down, if you like the car and everything else seems to be good, I would suggest you keep it and be pleased that you got the new PTU. However, I am a little bit concerned about your description of the transmission behavior. Are you having them check that out, too?
It would sure be nice to chat with the previous owner and get some history on the car. Is it possible for the dealership to provide that information? They might need to contact the previous owner and ask permission to provide that to you. I would also ask the dealer to run the oasis report on the car.