Saw it Thursday at midnight, dudes dressing up, it was a massive nerd fest.
Movis was a lot of fun. It had plenty of action, it was emotional when it needed to be, and it was genuinely funny as well. There was enough cheese to know you were watching a comic book movie and it didn't take itself too seriously and that's a good thing.
The thing that stood out for me was the genuine laughs. They weren't the lame one liners a la James Bond movies. There were some solid laughs with great timing. Thor's line about Loki being adopted was awesome.
One of my main concerns about Avengers going in was the distribution of screen time amongst the main characters. I didn't feel like any of the mains had too much or too little. Whedon spread it out nicely.
In regards to the secret scene
Solid movie, a lot of fun. 8/10