I'm not a fan of the original Avengers comic series, but I have enjoyed the two Iron Man films very much. And now I can't wait to rent "Thor" and "Captain America," so I can get the rest of the story. Avengers has a tight, humorous script, excellent performances, deep relationships between the characters, and it's almost unnecessary these days to say how awesome the special FX are. The story is intriguing, but not so complicated as to confuse people who haven't seen the previous films that lead up to this one. Having seen it both in 2D and IMAX 3D, I definitely say splurge for the IMAX 3D, even though the 2D is no less enjoyable. One word of advice... stay for the credits... ALL the credits. There's not one, but TWO extra scenes.
Pros well paced, great story, great actors, funny as heck