Managers are almost completely irrelevant. A poor one might cost you a game or two, but most of them make interchangeable decisions that even out over the course of the year. I don't think he's a poor manager, he's average, which is fine.
I hope Gibby wins, just for fun. I have little issue with his bullpen management as well as with his lineups and subs most times. We can all bitch about a decision here and there, it's the nature of the game, but all in all, he's fine.