Just saw Thor last night (I'm terribly slow when it comes to catching movies. Last movie I saw in theaters was Sucker Punch) and quite enjoyed it. I like the tendency I'm seeing with Thor and Iron Man for Marvel's movies to focus on just being fun. Not funny or silly but just enjoyable. It's a hard quality to define, sort of like the movie equivalent of a game of tag: a bit of excitement, some tension and a feeling of enjoyable exhilaration. Thor has less comedic moments than Iron Man but that's probably for the best. If you make things too funny then you begin to realize just how ridiculous all the Asgardians look. It's a refreshing change of pace from past comic-movies (and movies in general) which focus heavily on superhuman angst and drama.
Be warned, spoilers ahead.
I'm especially impressed with how the movie handled its antagonists. The SHIELD agents who swoop in, confiscate equipment, arrest Thor and otherwise get in the way are never shown as incompetent or malicious. In fact some of them (especially their leader agent Coulson) are downright likable. I even found myself kind of liking Loki, which was very surprising. You actually find yourself applauding some of his clever lies and misdirections and that's a great trait to have in a villain. Hopefully it's something they keep in future movies.
The movie wasn't flawless by any means. I wish there was more Thor being the God of Thunder rather than learning what it's like to be mortal. The fight with the Ice Giants near the beginning was fun (although the Ice Giants blend in so much with the background that it can be hard to see what's going on) and a great way to establish just how powerful Thor is. However the fight with the Destroyer was basically a non-event. It could have been a good opportunity for Thor's Asgardian sidekicks to show off how badass they can be but they just end up getting thrown around like ragdolls until Thor gets his power back and treats the Destroyer the same way. Thor's fight with Loki is more intense and extended but it takes place on a giant glowing bridge in space and without an environment to interact with there's little to give us a sense of power or scale to the conflict, especially since neither of them use much in the way of flashy moves.
The obligatory love interest is also annoying, mostly because there is absolutely nothing interesting about their relationship. They meet and fall in love in the course of a day or two. If they had played with the nature of the relationship a bit more they might have managed to create something worth watching. Maybe a hot-blooded god like Thor can easily fall madly in love with a mortal woman upon meeting her (fits the mythology for most gods after all) while things move far, far faster than she is used to. Or perhaps Thor's godlike charisma means that the mortal woman is instantly smitten with him while he remains relatively aloof (after all he's thousands of years old and she'll be dead in scant decades). But having the two of them just fall into one another's hearts makes it just another bad Hollywood romance. She's supposedly a scientist as well but you never see her do anything resembling it. She drives a car, she looks at some photos, she occasionally says the words "Einstein-Rosen Bridge". That's it. In fact, she doesn't actually do anything at all, she's not even the one who gets him out of SHIELD custody after he's captured. She seems to exist purely to kiss Thor before he leaves and make him sad when he can't go back to see her. I find the relationship between Thor and the senior scientist Erik Selvig much more interesting as he slowly begins to realize that legends are coming to life before his eyes.
But like I said overall I definitely enjoyed the movie and would recommend it for any comic fan or anyone who's looking to run a high-powered fantasy RPG (if you're playing Exalted and you need to explain the First Age to your players, just show them Asgard).