Pretty much, I would agree with SPS that it was a flawed film. An enjoyable enough experience, with some really cool moments scattered here and there, but nowhere near as good as the original. Which is a really darn shame, as this was the one film I had high expectations from.
My biggest irritation? They turned Justin Hammer, one of my favorite Iron Man villains in the comics, and took away all of the style, elegance, vision, and intelligence that made him interesting. The comic version of Hammer was a cold and ruthless industrialist who operates by offering people what they most want, and then using his deals to basically own them. He basically worked through manipulation, except he was always clever enough to evade suspicion. The movie version is pretty much a clown who tries to act like Tony Stark, but it utterly fails because his actor has none of the charm and charisma of Robert Downey. I hated this character every time he showed up in this film, and I frankly found movie Hammer so irritating that I'd have hated him even if I never picked up a single issue of the comic.
And the worst of it? Hammer gets manipulated. By Whiplash. With relative ease. This movie pretty much turns Hammer into a joke on every level, which is a disgrace considering that he's supposed to be one of Iron Man's top tier villains.
I will say that I found IM2's Whiplash to be an improvement over the comic version, but then Whiplash was never a character that made much sense to me. His motivations don't make a lot of sense here either... revenge is generally a pretty weak and limited motivation, but revenge against a dead man makes even less sense. That said, there's a lot to like in this version of Whiplash... he looks like a thug, but there's a calculating intelligence under the surface. Mickey Rourke plays the character very well in that respect. I also like the fact that the movie solves one of the main problems with Whiplash as an Iron Man villain... namely, his inability to physically hold his own with Shellhead. All in all, I'd say he's an improvement.
Oh, yeah, and to expand on one point, this movie is way to crammed with ancillary characters. Black Widow, for instance, is basically irrelevant here except for the ending, which could have been resolved just as easily by someone else. It's the same problem that plagued movies like Wolverine: Origins, which bogged the story down with people that don't contribute anything. Just tell the story and use those characters you need to make the story work.
For the rest, I'll just agree with SPS in his assessment of the problems in this film. Except to say that I actually quite enjoyed the Senate hearing scene, and thought Gary Shandling (who I actually am not a fan of) did a very nice job playing the slimy Senator.
So, yeah. Good experience, but inferior to the first film.
Sad thing is I enjoyed Black Widow in this film even though she was mainly there for eye candy.
Oh and I agree had they pared down the cast a bit (IE getting rid of Black Widow, and Justin Hammer or at least make him not get definitvely defeated, and a joke like Gray said), and tightened up the first half or so of it, it could have been really good.
I really wanted to see more of a focus on Rhodey in this one, as I thought the character they had built him up as in the first was pretty good. As it is we only got a glimmer of the idea that Rhodey was the second fiddle to Tony.
What I think is funny is that the first one's first 3/4ths were really really good, it was only the film's climax that suffered, this film is the exact opposite IMO. Its like the scriptwriters had forgotten what worked about the first one but listened to the biggest complaint.
Also Sam Rockwell is an amazing actor and he shouldn't have been wasted in this role.
I kind of thought Mickey Rourke was just there as Whiplash. He is another good actor, but I never got attached to him, like I did to Obidiah Stane in the first one.