I was somewhat skeptical going into this. I was really afraid that it would suffer from the problem that most superhero movies do. The first movie about a new superhero almost always gets bogged down in exposition and understandably so - they have to explain how they got to be a superhero in the first place.
Iron Man handled this exceptionally well. I got plenty of background and origins and still had time for a big battle with the villain at the end.
I may have to see it again while it's still on the big screen. The effects were flawless and the action sequences were some of the best I've seen. In short: go see it!