(The top portion of this review will not contain spoilers. However, if you have seen the movie or would like to hear a few more specifics, I will go into details below. That section will contain significant spoilers)
In a way, Avengers: Age of Ultron is the Iron Man 2 of the Avengers series. It makes a lot of the same mistakes as IM2 did, primarily by trying to stuff in too many plot elements and sequel set-ups for the movie to come together as a cohesive whole. You can feel Joss Whedon stressing out over the movie, as more and more things get piled on while he tries to wrangle a decent Ultron film out of it. I counted at least ten different stories and new character/place introductions in the first half hour alone.