Sorry to bump, but since this IS the topic for it...
Just watched it. Having seen the original, this one seemed a bit underwhelming. I'd say the humor was really good here and i think there was more action overall. But i thought the story wasn't nearly as good. I found the main villain to be very bland and typical. The story was WAY too hectic. It sounded like all the actors were trying to cram as many lines in 5 seconds as possible, speed talking, way too fast. Story overall felt rushed. I hate to bring the crap known as Transformers 2 up, but the speed talking reminded me of that movie. In regards to the story, far too much going on at once. I feel like the overall story felt like they were trying to do way too much within the confines of two hours.
I'd say the action was much more lengthy and more widely dispersed through the film. But i also feel that what little action there was in the original was a lot better in terms of characters thinking by using clever means to beat their opponents.
Actors were all great. Scarlett Johansson was hot of course, but kind of just there for hotness alone. She gets one scene where she gets a Matrix-like fight which was pretty silly but cool of course. Kind of completely unnecessary though. Robert Downey Jr is great as always. Glad we get to see more of Samuel L Jackson as Nick Fury too (and not just an after credits thing). Only character i really didn't like was that Hammer CEO guy. I don't know his role in the comics, but he was a very annoying pussy to me, typical snot faced rich jackass (but not cool, likable, and funny like Tony Stark). The villain was cool and well casted, but was again quite bland with predictable motivations and actions. I blame poor script for the villain, not the actor or character.
The first one is far better in terms of story and even action. About the only thing i think IM2 did better was the humor, i laughed out loud many times. There was more action here, but at the expense of less refined action. A predictable villain, and no surprises around the corner. Story was way too rushed along. It's not a BAD movie by any means, just inferior to the original which it had to live up to. It's entertaining however, and i think anyone who wants a decent superhero film will enjoy it. Just don't expect it to be as great as the original. Overall, i'd probably give it a 7.5/10. The original was a solid 9 to me (and it is one of my favorite superhero movies, so hard to top).
Sorry for long post, but no one else seems to have seen it nor has anyone posted any impressions.