Just saw it... It was great. Up there with the first Iron Man for sure.
I'd love to see the new Amazing Spider-Man also take place in this "Marvel movie-verse"... But here's to hoping!
Whedon did an amazing job (as always). Some of the reviews I've read were that Hawkeye was underutilized... but I think that he came out being the biggest badass of them all. No superpowers whatsoever and he held his own easily (better than Black Widow, but then again, she was a spy and not a soldier).
Also, Mark Ruffalo = best Bruce Banner. By far. He had that right amount of charm, charisma, and depth to pull off the character. He came off as challenged yet not too mopey. And the Hulk was a riot. That's how the Hulk should be: vicious, animalistic, and quick.
LOOOOOOOVED IT.