I don't want to get too spoilery, so i'll just say that there was lots of cool action (of course,) lots of amusing humor, i was impressed that a lot of the people in the movie were relatively genre savvy, and the motivations and development of the bad guy are handled pretty well for something as short as a movie.
The only nitpick i have is that Thor and a lot of the other gods were probably not even born at the time of the first war with the frost giants, which supposedly resulted in the Norse mythology on Earth. (They certainly weren't old enough to remember it anyways, filling in the back story at the beginning of the movie is presented as Odin giving a history lesson.) So how is it that Earth has detailed legends about them that just happen to match their actual characteristics?
But that is a very minor nitpick, and aside from that it's a pretty good movie :)