I'm the guy who sees a movie onces in theatres and then buys it when it comes out for home viewing. Not the Avengers, I saw it twice and believe me, it is an awesome film.
My one big worry was that with so many main characters, Thor, Iron Man, Captain America and the Hulk etc in one film, that one particular character would take over most of the screen time. This was not the case!
The film does it all right, despite the simple plot, which is a good thing as it allows us to focus on the team coming together, it flows well and manages to sustain multiple viewings.
I have already preordered this, I did the day after I saw it and saw Mightyape had a page for it!