I have no affiliation with the Falcons but I think what Petrino did is just bad business. If you want to quit, why not just wait until after the season? There are only three games left. He quit on his team.
I understand this was his first year there and he thought he would have the opportunity to work with Michael Vick but I just don't like leaving your team high and dry like that. Clearly, he realized that he was not suited for the pro game. It appeared that he could not control his locker room and certain players. Sure, it has been a tumultuous season but that is why you are the coach and that is why you are paid the big bucks...to LEAD! He couldn't do it and I think it is just poor character to abandon your team and the owner that gave you an opportunity with only three games left.