Just saw this in the theater yesterday. I have to give The Avengers an A+. WOW. What a terrific picture. The action is nonstop, the plot tight, and the characters larger than life. Mark Ruffalo does a terrific job as Bruce Banner. Robert Downey Jr. as Iron Man is snarky and fun. Evans, Johansson, Renner, Hemsworth and Jackson nicely round out the cast. They all have equal screen time, so the movie is never the Iron Man or Captain America show, but a true melding of the Avengers. And a big shout out to Tom Hiddleston, who does a terrific job of portraying the evil Loki. Man, I really hated that guy at the end.
Another winner from Joss Whedon, the movie has action, humor, drama, and adventure wrapped in a bow. It's violent, but that's to be expected of six superheroes out to save the world. If you haven't seen this, I highly recommend it. I plan on seeing it again, it was that good. I also watched it in 3D, though I hadn't planned on it at first. But I'm glad I did. It actually added to the experience. I think I might take my kids later this weekend. It was violent though, so I'm going back and forth on that. But I did take them to Captain America, and they were fine with that.
So to recap, (Marvel's) The Avengers A+ .