Robert Downey Jr. is one of the finest actors ever. His interpretation of Iron Man is consistently engaging. The script is interesting, and the film isn't overloaded with special effects -- although it does get kind of cartoonish at points.
Jeff Bridges does a great job in his role, it's quite the contrast from his portrayal of 'the Dude' in The Big Lebowski. Gwyeneth Paltrow is kind of wasted in her role as an assistant, and the love connection between her and Robert Downey Jr. is less than palpable, but it's not distracting. In fact, all the supporting cast does a passable job, they're a little low-key, but it fits the tone of the movie.
There's a teaser clip at the very end of the credits, so stay through the whole thing, OK? It looks like Stan Lee is going to do Marvel Comics tie-ins between all the movies. If done correctly, it could be a great decade or more of fantastic movies.
Movies on Whidbey Island.