This was great enormous fun! We were going to go opening week-end, but that didn't work out, so we went last Tuesday at 12:30. We were surprised at how crowded it was.
The Avengers is directed by Joss Whedon and stars Robert Downey, Jr. as Iron Man (our family's favorite of these heroes), Chris Evans as Captain America, Mark Ruffalo as Bruce Banner/Hulk, Chris Hemsworth as Thor, Scarlett Johansson as Black Widow, Jeremy Renner as Hawkeye, Tom Hiddleston as Loki, Clark Gregg as Phil Coulson (who has been with us through the other movies), and Samuel L. Jackson as Nick Fury.
It's getting great reviews. links to some of those are mentioned in the Wikipedia article. Rotten Tomatoes has it at 93%. It's breaking box office records.