I went to see Thor: The Dark World last night and was really impressed. Similar to the first one Thor was to save Earth and Asgard from a villain that wants nothing else but revenge. It picks up after the events in The Avengers, which is also brought up in the movie. Loki is still hell bent on getting revenge on Thor and Odin, but wants to help Thor fight and kill the Dark Elves, especially Malekith after (SPOILER ALERT) he kills Thor and Loki's mother.
The film had a good amount of humor in it so the viewers aren't just sitting there with amazed looks, because of the special effects. Thor breaks out Loki to go and battle Malekith, shortly after they bicker back and forth just like brothers do. Which I enjoyed quite a bit, another Avenger even has a cameo when Loki changes into a certain hero to tease Thor. (I'm not saying who, but it was hilarious in the movie.) Dr. Erik Selvig is very funny in the film after have his brain taken over by Loki in The Avengers, he has a few loose screws in his head which makes him kind of crazy in the Thor sequel.
The one thing I was mainly paying attention to was the hidden "easter eggs" in the film. It's not a Marvel movie until there is a hint of another hero or villain in the film. Which there is, and I'm not telling what they are. That was mean yes, but can't ruin the whole movie for you. Although there is a mention of Dr. Strange, it happens very fast and you have to be a die hard fan to know what they are talking about. The film was great! I think better than the first one. Characters are enjoyable and the story is loaded with action and mystery. Loki is still evil, but you sense a change in him in this film. I would highly recommend this film if you have seen the other Marvel movies.