First, and I think you should keep this in mind, Iron Man is a fun action movie directed by guy, Sean Black, well-known for fun action movies (Lethal Weapon being the prime example). It has a pleasingly asymmetrical plot, lots of impressive SFX, and veritable police line-up of despicable villains. It doesn't do anything particularly new and its big "twist" is fairly low-key. As a matter of fact, the entire movie seems like an elaborate exercise in establishing the proper scale of an action movie.
Right off the bat, Tony Stark (played with with a bit more roiling pathology than his last time out in the Avengers) listens calmly as his friend and fellow exoskeleton pilot Col. James Rhodes explains a series of bombings ascribed to an arch-terrorist The Mandarin. Stark suggests the problem is one for the President and the military rather than the Avengers and the Shield Organization. The suggestion here is that Iron Man is concerned with threats of a truly global scale, not the terrorist of the week. Then Stark rushes outside in a full-blown panic attack.
You see, one of the smartest things about this movie is how it picks up on the near-death experience Stark suffered at the climax of last summer's Avengers. In an effort to seal off a worm-hole funneling alien invaders into New York City, Iron Man flew between worlds to deliver a nuclear warhead. The resulting explosion sent him tumbling lifelessly back to Earth and even at the end of the movie, Stark seemed shocked by his own mortality.
In Iron Man 3, Stark is suffering from bouts of anxiety and insomnia, conditions exasperated by an ongoing exoskeleton building binge. By this point, Stark is on his 42nd version of the suit, and is examining how to create a suit that can disassemble itself and fly independently to link with him. The lack of sleep and manic bouts of engineering has added stress to his relationship with Pepper Potts, long-time assistant and current SO.
Perhaps because of this added stress, Stark makes an ill-advised revenge threat against The Mandarin when one of his attacks results in the injury to his friend Happy. Within short order, Stark's mansion is under assault from rockets launched by helicopters.
This gives way to one of the movie's two great scenes of spectacular mayhem. I watched Iron Man 3 in full IMAX, and the rapid structural failure of Iron Man's cantilevered mansion is truly cataclysmic on a three story screen. One thing that really shows how far CGI has come in recent years is watching the seamless integration of the actors' movement tracked to the larger scale disintegration of the building in front of a typically epic California sunset.
Another appealing aspect to this movie and honestly the one that stuck in my head far longer than I thought it might, is this question of Stark's role as a hero. Iron Man unquestionably saves people and does typically altruistic things. However, and this has been an aspect to the character from the first movie, he does these things in the full light of day. "I am Iron Man," has a very different meaning in these movies than the masked vigilante of Batman saying essentially the same thing. Bruce Wayne's pronouncement is the threat of the unknown, Stark's is a fairly brave recognition of the truth.
After all, it's not like Stark couldn't keep to the shadows. The government was more than happy to provide an alibi and cover story for him. Stark already chose to tell his enemies where to find him a long time before he gave them his actual address. And while Iron Man and Tony Stark kill an awful lot of people in this movie they do so in view of the public. Perhaps no one other than another Avenger could really hold Stark accountable for his actions but it's not like he hides what he does. The movie takes the time to draw parallels between Tony Stark's self-aggrandizement and the movie's villains need for control and power. Really the only difference is that Stark is all too happy to remove his mask to take credit and blame for his actions and The Mandarin finds elaborate ways to hide his true identity.
The Iron Man movies seem to suggest that what really separates a hero from a villain isn't so much the methods or motives but the willingness to submit to public scrutiny.