Every geek I know had a heart attack when they saw Hulk catch Iron Man.

This should be interesting. I'm typically skeptical when there's so many "protagonists" in a story (will there be a single main character here?), not to mention I have no idea who the overall antagonist is (I see the guy from Thor) - but... ...the trailer demonstrated something even more important: there will be much conflict between these protagonists and that's what is going to propel the heart of this story - not who the bad guy.

Joss Whedon excels at writing big pieces with lots of characters. Serenity, Buffy, and Astonishing X-Men have proved he can pull it off. I might be a bit too excited for this.

Trailer looks awesome!! And it seems to remedy a large problem I had with Thor. I didn't like that the main conflict in Thor was that he needed to protect his homeworld from the Ice people (sorry - not a fanboy) when it would have been a stronger conflict for Thor to protect earth. It made the film have a strange split in focus that I think weakened it. But from this Avengers trailer, it looks like the villain is Thor's brother Loki - who is now attacking earth. So it's probably the case that the Thor plot suffered to save the bigger battle for the Avengers film. I understand them making that choice. One of my all time favorite story tropes is when a group of strangers unite against a common threat. For some reason that's a direct line to my emotional core. So I will eagerly see this!