As Thor, Chris Hemsworth was right on the money. He had the swagger, the confidence, and the charm that the character needed. He played very well with all of the other actors, especially Anthony Hopkins as his father, and Hemsworth also had the massive physical presence that is required of an actor playing a Norse God. The sequences in the mythic realm were beautiful and epic, with the rainbow bridge from the comic mythology stealing the show. And what's even more important, I thought that Thor as a character fit very comfortably into his larger-than-life mythic realm.
However, the sequences here on Earth seemed forced and/or phoned in. Natalie Portman plays a plucky scientist with a plucky assistant and a plucky advisor. And it's a good thing that she was working with people; otherwise she would have had no one to talk to in order to deliver exposition. After Thor is banished to Earth, loses his powers, and it taken down like a chump by S.H.I.E.L.D. agents (spoilers!), he spends approximately six minutes of screen time "learning" his lesson and going on the hero's journey. He comes back, says he loves Natalie Portman, which doesn't really seem all that likely.
The other problem with the film involved the action sequences. A lot of them were blindingly blurry, incredibly quick, and I'm prepared to lay some of that at the foot of the the post-production 3D effects. But even without those 3D effects, the over-reliance on CGI landscapes and CGI cannon-fodder made the shots a little difficult to process. It's a running trend in films nowadays, but it is one that doesn't seem to be going away.
Overall, I liked the film. Don't get me wrong. But it felt like a prequel to Thor's appearance in "The Avengers," much more than it felt like a film designed to start a Thor series. I'm not the biggest fan of the Marvel comic universe, but I like watching how their film universe is developing. I just wonder if they are putting the cart before the horse, though. These films need to stand on their own first, and encourage the overall universe second. If they only serve as prologues to the massive team-up film, then that puts an awful lot of eggs in one big-budget basket.