Saw it last night, thought it was a very entertaining, solid movie. Robert Downey Jr. was possibly the most charismatic and well-cast actor in a superhero role I've ever seen. But that might be hyperbole on my part. Jeff Bridges, while excellent in most scenes, I think had trouble with a few scenes, particularly the one where he started yelling at the engineer. Seemed awkward. He also seemed pretty awkward when he was exposed in his suit at the end.
There were also a number of scenes, particularly in the mid to final part, that were either badly acted or badly written, but didn't take away too much from the movie. Except for the cringe-worthy line from Gwyneth Paltrow "My card's not working. What's that thing? Some kind of device? Is it going to pick the lock?" pretty much delivered as unnaturally and quickly as possible.
Also, the entire climax to the film felt like it wasn't properly built up to. I was just thinking throughout the whole climax "They're really doing it right now? It feels so awkward at this point." which was kind of nagging. They probably could've gone longer and put a little more material in there, properly (at least in my opinion) built up to the climax.
But as I said, Downey Jr.: EXCELLENT. Any scene with him in the finished suit?: EXCELLENT. Final hidden scene?: EXCELLENT. Origin story portion of the film?: Pretty damn solid. And the opening scene was perfect as well.
Overall, definitely a worthwhile film.