Although this movie had its flaws I thought it was the best of the Iron Man movies so far. I thought the entire movie was thrilling, entertaining, funny and easily understood. I felt on edge the entire time. Even my wife, who isn't a comic book movie person, liked this movie in comparison to the first two.
WARNING - MAJOR SPOILERS: Like others I would have liked to see more action from the new Iron Man machines. I didn't like how weak they seemed though. In the first and second movies it took quite a lot of fighting/damage to destroy one of his suits whereas in this one we see a lot get destroyed in just a few min. My biggest objection to the movie was when he destroyed all of his suits less than a minute after killing his enemy when throughout the movie people who seemed to be dead weren't actually dead (forget the fact that at any time aliens and a whole bunch of other bad guys could easily attack and these suits might come in handy).