Also had it happen. Turned out that the passenger door lock somehow got jammed. When I tried to unjam it, the plastic piece of the lock that you pull up came off. I carefully guided it back into the slots that house the plastic pull. While right now the passenger can't unlock the door, even if it weren't broken, it's a PIA to reach back there and unlock that it really doesn't matter. However, locking works fine, and since I park in the city, I need that security.
This is the only problem that I have had with the GTO so far, so I haven't taken it back to the dealer, since it's so minor, and I'm more concerned with them doing more harm to the car than fixing it. In fact, the car hasn't been back since I drove it out of the lot.