The sequel for the most part works pretty well they keep a lot of the same relationships and attitudes that made the first one great and introduce more in the way of action. The enigmatic shield pops up more and there is more teasing about the avengers initiative that since I'm not really a comic geek doesn't get me worked up, I'm sure when a film comes out of it I'll be more than happy to peruse the results.
The cast is pretty solid and the new additions blend in fairly well with Sam Rockwells egotisical Justin Hammer trying to userp stark's ironman tech and the bitter and twisted Ivan trying to avenge his father and kill of Stark. They also swapped out the actor playing roadie which though the new guy is still good just felt a bit odd as far as the relationships went he came off as a lot colder and more serious which was a slight tonal shift for the character from the first film.
All in all its a very good film that suffers a bit in the pacing, there is a lot going on and at times it looses some of the slick streamlined pacing that the first one managed.
Still well worth seeing and a great film highly recomended