Watched it tonigth with my daughter. She saw it once already, but this one was different for her because it was in 3D. She admitted after that 2D was better, and I have to say that I found the 3D imaging a bit distracting during fight sequences.
As for the movie:
It was a good movie. I won't go so far as to say great. It was definitely better than both the Thor and Cap (shudder) movies. I enjoyd it, and as a bonus it even made me laugh a few times. Mind you, coming from Joss Whedon, i shouldn't be surprised.
Was it the best movie I have ever seen? Hardly! But, for what it was, it was entertaining. I thought the Hawkeye character really blew, that was a major disappointment. There were also a few slip-ups, like Hawkeye running out of arrows and then next time you see him his quiver is full again, that sort of thing. There was also a line delivered to Dr Banner about him being the only good authority on gamma radiation that i found annoying, as off the top of my head don't both Dr Langkowski and Doc Samson know quite a bit about that subject as well?
Anyhoo. It was better than i expected it to be. Still wouldn't call i great, just 'pretty solid.' After seeing X-Men First Class, everything superhero-y will be judged according to that great movie, and Avengers was definitely a step or two below that.