It seems to me that while it is a lovely notion that everyone on this team loves each other, the fact remains that talent wins titles and the Celtics beach is lacking talent. I don't think it is essental that there is a team love fest. I think it is essental that when they are on the floor they play together as a team, but they do not have to be best friends off the court.
In Marbury's case, the fact that he has a career average of around 8 assists tells me that he can share the ball. 20 point per game tells me he can score. To be honest, i haven't watched enough of him to have an opinion on his defense.
My point is that team can win that don't get along that well off the court. It's a pretty well known fact that Bird and McHale didn't hang out together once the game was over.
Now I don't know if Marbury would fit here or not, but with the state of the bench as it is, I'd give him a shot. And who knows, maybe he'd even get along with everyone.