The first movie was a light-hearted fun telling of the origins of Iron Man. This time around, the movie has taken a darker tone in storyline and visually. Alot of the bigger action scenes in the movie occur during the night time hours. Behind Tony's carefree persona is a man who has to face his non-invincibility and failed expectations from his father. And, to pile things on top of that, the government wants possession of the suit for the defense of the the country. Another person is seeking revenge for what Starks father wrought upon his family. If that werent enough, his competitor, Justin Hammer, is seeking to usurp as many government contracts to bolster his own company. As you can see, there is alot going on in this movie and some may think too much and that it looses a bit of focus
It still keeps its funny bone well intact but it seems quite a bit muted than before. Stark gets alot of the best lines. The banter/arguments between Stark and Pepper provide some relief from the more serious moments. Rhodey pitches in with a few lines of his own. Gary Shandling, where has he been, plays a wonderful foil in the character of a Senator leading the attempts to procure the suit. Justin Hammers flamboyant protrayal adds a bit of levity.
But, most would come to see the special effects and the action scenes. Again, these are more muted and less prevalent than in the previous incarnation. It waits to deliver the big bang at the very end of the movie. The CG is done well but, at times, the odd motion of the characters reveals the true source. As I recall, there seemed to be only 3 major action packed moments. Also, stick around after the credits for a special trailer and keep your eyes out for cameoes and special references
For diehard fans, this would be a must see. However, I think this would be worth the bargain matinee but not necessarily full admission.