In my opinion, humble or otherwise, this is one of the best Marvel movies.
For once, the trailers don't give away the story. The trailers consist of shots from several action set pieces from the movie but really tell you nothing about the story.
Samuel L. Jackson has a lot more to do in this movie then we've seen of him, as Nick Fury. You've probably seen the trailer where he's being shot at by what appear to be the DC police.
The story in a general sense is about how much of our actual freedom are we willing to give up to the people who are supposed to be protecting us. Actually, the movie is about how much of our freedom should the people who are supposed to be protecting us, take from us without our knowledge, to protect us. A very real issue in these days of NSA spying. And then, how can our enemies, who are trying to destroy our freedoms, exploit that tension between us willing (or unwittingly) to give up some freedom for protection and our desire to remain free.
The special effects are just amazing as you would expect. We saw the movie in 3D and I'll say that the 3D was so good that I mostly forgot that I was watching it in 3D.
You don't go to a movie like this expecting to Oscar winning performances and you won't see any here. The acting is adequate to the needs of the movie. Robert Redford is pretty good as Nick Fury's boss (Nick Fury has a boss?). The movie tries desperately to develop some rapport between Chris Evans' Captain American and Scarlett Johansson's Black Widow but pretty much fails at that. There is much forced banter between them where she suggests girls he can date. Anthony Mackie is pretty good as the Falcon, he does actually provide some comic relief that actually works. The special effects of him flying around however, are probably the weakest in the movie.
There are some pretty intense scenes in the movie, like the scene between Fury and the DC cops (which goes on forever) which I suspect would upset younger children. The movie isn't rated PG-13 for the sex (there isn't any) or the language (remarkably subdued) but the violence. The movie attempts ro interject some moral ambiguity (which I'm sure the ratings people don't care about) that might be confusing to kids. And I'd estimate that about 50,000 people get killed, fortunately most of them off camera.