Daughter and I just back from seeing Avengers Assemble (aka Marvel's Avengers or probably half a dozen other titles: hell, it's the one with Iron Man, Hulk, Captain America, Thor, old Uncle Sam Jackson and all, directed and scripted by Joss Whedon, OK?)
What can I say? I'm not normally big on superhero films, but this is no normal superhero film, and courtesy Mr Whedon it has a phenomenally witty script. Also great performances: the review here reckons Loki steals the show, but I always have a soft spot for Robert Downey Jr. As the review says, he's like an Aaron Sorkin character, than which there can be no higher praise.
Go see it.