T.O.D.
My biggest problem of going to the theater now, is sitting in the audience. I want to be up on the stage doing, rather than watching.
Other than that, all of the things that BK mentioned, plus late arrivals. I know things happen.... car accidents, late babysitters, traffic; but some people just make a habit of running late to everything. And most theaters don't follow their own rules about latecomers being seated only during the breaks. They rush them down (usually they are in the first ten rows) and instead of being extremely quiet, everyone is saying excuse me as they get settled. It happens at movies also, but at live theater it is so distracting, not only to the rest of the audience, but to the actors trying to perform onstage.