^ I see what you're saying about the computer aided helper, but at the same time there were a lot of levels where he/she wasn't present and would have interfered with the pacing and feel of the game (consider the section set in the Tibetan mountains where the train's just crashed and an injured Drake has to make his way through). How would sections like this be affected with the inclusion of a second player?
I'm not against it per se, I just feel Naughty Dog should do what will serve their story and gameplay needs first, if c0-op servers their design for Uncharted 3, then go for it, if not, I'd rather not try to make it fit.