Great action, Robert Downey Jr. is good as always. Mickey Rourke is great as the villain. Of course, great effects.
The part of the plot involving Scarlet Johanson and Samuel L. Jackson seemed totally unnecessary, and really didn't fit in with the rest of the movie. I brings the level of realism down, and just doesn't make sense.
Also, when Rhodey basically sells one of the suits to Tony's rival, it doesn't seem right.
For what it is, I thought it was a very good movie. Lots of action, good special effects. I agree with the other reviewers that sometimes it's hard to tell what's going on in some of the action scenes. The director might have gone a little too far with the "realistic" camera work. Yes, there is some goofy humor and some corny scenes, but I think they mostly work. If you're looking for a good action movie, this is worth seeing.
There's lots of action from beginning to end. The performances are good, if not great. Special effects are top notch. The story is interesting, with a moral struggle, corporate greed, and a love interest. No real surprises, but a good straight-ahead plot. I took my kids, aged 9 and 12 to see this, and there were a couple of scenes that were maybe not entirely appropriate for a 9 year old. There are some adult situations and some cruel violence.