Sorry for bumping this thread, but I just watched the movie, and I had to give my thoughts:
Oh fate, this cast was awesome. I have never seen such an incredible cast of characters before in my life. Hiddleston, in particular, had a masterful performance as Loki. He really stole the show, in my opinion. The humor and seriousness were combined spectacularly, and the differing personalities of the Avengers was brilliant as well. I can honestly say that there wasn't a single character that I didn't like. You know, even the very minor characters were great. The old German man was probably my favorite out of all of the minor characters, but there were several other great ones as well.
This movie is worth watching at a theater, and when it comes out on DVD, it's a movie that I'll probably buy as well.