I saw the movie last night in IMAX. No spoilers here. The place was packed and the anticipation was huge. A guy dressed up as Joker did a little wrestling in the front with a guy who was wearing a Batman cowl while waiting for the movie to start. This was not rehearsed and these guys didn't come with each other, so that was pretty funny. I have to say that the Imax screen was probably only too big for the action and actors maybe... three times. As in you were like, that's huge. And I think all of the times was when it was the actual Imax sized footage, not the standard aspect ratio. Also, there was maybe only one or two times where the changing of the ratio even noticablly drew you out of the movie and made you go, whoa, that just changed a lot.
Needless to say, I am of the opinion that it should be viewed in IMAX because all of the city scapes were filmed in it and they look gorgeous. And no, even if you are super-hyped for this movie, you will not be let down at all. A truly wonderful film.