Just saw this today and it exceeded my expectations.
There are many things I totally love about it-- like for example, their initial problem with teamwork. I love that they all had to go through it; it turned the storyline into something more believable than just being about a bunch of cool dudez fighting teh evil togetehr FUCK YEAH!!!1
And like many fans I was pissed that Norton is not playing Hulk, I really thought he has an inherent contrast with the character, having a small frame and little voice and all. But Mark Ruffalo delivered, in fact I just noticed that he does have an inherent difference with the Hulk as well, and that is being softspoken, delivering his lines in a gentle, almost lazy voice as he does in his other movies (yeah, I notice stuff like that).
And perhaps the greatest achievement of the film concerning me is that it made me love Tony Stark's character. Sure I appreciate his being snark and all, but I prefer my superheroes flawed and insecure, so I didn't care much about him. But somehow I grew to like him in this flick and I'm certainly watching Iron Man 3.
Lastly, I can't help but agree with you guys about Capt. America. It's not that he wasn't given enough screen time, it's just that his scenes lacked impact. The only scene of him that I found moving is when he assumed leadership and started giving orders to the team. I also think his inability to fly contributes to this, I mean, FFS, Iron Man and Thor can fly, Hulk can jump, BW managed to have mid-air screen time and Hawkeye was on top of a building. And where was Cap? Forever fighting on the ground.
And yeah, I know there's gonna be a scene mid/post credits but my bladder is going to burst so I had to go.