Overall, I liked it. It's a straightforward movie, and plays as such, but that's fine. It's well-executed for what it is. It's not meant to be the highly-complicated "who will make the next move?" type movie. It has a villain, heroes, an in-the-middle guy (Loki), and believable actions from everybody.
Really, the biggest negative about a lot of these movies is how f'n stupid multiple characters usually act, which is what then advances the plot. Here there is no such easy spot to point out. The villains AND heroes do not act like idiots. So that's good.
Good action, funny in the right places, interesting in the right places (Thor + Loki banter is great), and a fair story. Not flawless, but it doesn't need to be. Not the best movie ever, but a "good" movie.