While I felt most of the casting choices were spot on throughout the film, it suffers from a poor script and weak plot that never really gets off the ground. This film should have been rewritten to contain a more substantial plot that was not only being used to set up the character for The Avengers movie, but to establish this character as a stand alone franchise.
Most of the scenes spent on earth contain typical comic book stereotypes that really were the ultimate unraveling of the film. Unlike DC's Green Lantern movie, I quite enjoyed the scenes spent in the outer reaches of space. The visuals have a unique feel and seem a bit different from most other Marvel movies. In essence, much more time should have been spent in the realm of Asgard. It would have made for a much stronger movie.
While I didn't hate Thor, I can honestly say it could have used some major tweaking. Marvel once again hit the mark with X-Men: First Class this past summer. It's too bad that Thor didn't succeed on the same level.