So last night I went to see The Avengers in IMAX 3D. (got the tickets online and I could pick the seats so no trouble getting in!)
Anyway after 2 hours and 30 minutes of watching it, and getting out of the theater at 1 A.M.

, I would say its most definitely worth going to!
Its funny (some moments the entire audience was laughing like you would expect at a comedy), has a good plot, the characters all work great together, and the action was not overdone. But still I would say its a great action movie, but wasn't constantly happening. Only a lot near the end and a bit spread throughout. So not overdone like some movies are.
So I would recommend this movie to anyone, IMAX or not. And make sure you stay right to the very, very end of the credits. The clips are worth seeing!