Just got back from seeing Iron Man 2. I liked it a lot, it had fun set-pieces, balls-to-the-wall action, funny dialouge, and plenty of charm, primarily provided by RDJ. Almost outshining him was Rockwell, though, who goes all out with his crazy I-think-I'm-loveable-but-actually-I-come-off-as-a-douche persona. Rourke did a competent job as Whiplash, but the role doesn't demand much. The female leads were kinda stiff, but L. Jackson was being L. Jackson to the fullest.
There were plenty of nerdy shout-outs, and my even-geekier-than-me friend ended up squealing several times, especially at the after-credit scene. Overall it's not as strong as the first one, but I love that movie a whole lot. If you like Iron Man, you should see this film.