It was great. The Hulk-Thor fight scene was boss, as was all the action. That's what stuck out to me, though. It was as awesome as I could have wanted it to be, which was pretty awesome.
Oh, there were some moments where it looked fantastic, to be sure.
But the problems that are generally associated with 3D seemed particularly pronounced. Some of the darker scenes were so low-contrast that it was hard to tell what was going on, and fast movement in the foreground was really juttery, to the point that it gave me a headache. I found myself taking off the glasses during the non-action scenes, and the scenes not featuring Scarlett Johansson's butt.
Wasn't her butt fantastic? I saw the movie last night with a huge group and afterwards the first thing that got brought up was how nice her ass was. I couldn't disagree. The whole movie was great. I was surprised at how funny it was. It was incredibly well done and all the superheros shined.
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When choosing between two evils, I always like to try the one I've never tried before. - Mae West
Also, it was really impressive how the movie was able to give every main character (even the second-stringers like Hawkeye and Black Widow) their due, without it feeling crowded or rushed. It was perfectly paced, and each main player got some solid character and story moments.
I thought Black Widow's backstory was a bit forced, but overall I agree with that. This has been said already by everyone who's seen the movie, but Mark Ruffalo really triumphed as Bruce Banner.