I do not have to say how amazing this movie is, as you should already know that. But, this movie was done really well. I would say this movie is the funniest out of the 3 total. Robert Downey Jr. deliveries a tremendous amount of one-liners. This really does just add more awesomeness to the movie. It made this movie (out of the 3) much more funnier.
There were some flaws in the movie as there are in any. I would not recommend seeing it in 3-D. There really was no point in the 3-D affect.
The last thirty minutes of Iron Man 3 is an adrenaline rush for your mind. It is full of action pack moments with all of the characters. It keeps you biting your nails wanting more. The whole movie builds to the end thirty minutes, which isn't necessarily a bad thing. But without Robert Downey Jr. as Tony Stark, the whole first part of the movie would not have been any good.
Robert Downey Jr. is the only guy who can be Iron Man, and make this movie great.
What would I have Changed? (Spoilers)
Well don't get me wrong Gwyneth Paltrow is a great actress. But Tony Stark is the guy who would at least have a younger lady. I could see that part being played but someone younger. I would have also added more action scenes. As there were 3 or 4 main ones, I would have added more. I also would have had Tony talk about the Avengers as they tried to steer clear of that topic in the whole movie.