There's not much I can say that hasn't been said already. This movie was absolutely phenomenal. The right balance of screen time and development for each major character in the film, the perfect mix of action and dialogue, and the perfect blend of comedy and seriousness - a movie I'll definitely see over and over again. My only criticism - Nick Fury seemed to be less than awesome and a bit overshadowed by just about everyone else in this film, considering he's the leader of Shield, and is supposed to be pretty bad-ash on his own. But even that's understandable considering the characters by whom he was surrounded.
Bottom line, run don't walk to see this movie - 150% worth the price of admission!
Pros well paced, great story, great actors, fantastic action, phenomenal special effects