Thor: The Dark World. Shortest possible review: really good, definitely worth seeing.
The film not only picks up after the first Thor film, but also ties up some of the loose ends from The Avengers, wherein Thor was a major character. I like that they're maintaining the continuity across so many different franchises (or is it perhaps sub-franchises?), and that they're doing it so well.
Thor's look is a little bit different in this film, specifically in terms of his hair, which now sports some subtle braids. That's one of the things that marks the film as a whole; there are a lot more nods to Norse culture throughout, from the ubiquitous knotwork to the runes we see on Loki's collar. Even the ships, which can fly, can definitely trace their visual lineage back to the longships of the 10th century. We also see a lot more of Asgard itself, and it's much less a "sparkling pipe organ" that we saw in the first film. Much more texture and a feel that it's a real city, albeit one created by a culture technologically superior to our own, and with its own aesthetic sensibilities.
The pacing of the film is spot-on. It is very much an action film, with almost no slow parts in it at all. If anything, I might have appreciated just a tad more exposition, specifically as to why the bad guys are doing what they're doing, but fortunately the central story - the relationships between Thor and Loki and Thor and Jane Foster - is served quite well by the script.
The film's tone is light, even though the stakes are higher than they've been in any Marvel movie to date. This isn't to say that the film is goofy, but it's nice to know that one can take a superhero film in a direction very different from Christian Bale's Dark Knight films and not end up with Batman and Robin. The dialog I thought was very snappy and sounded perfect coming out of the character's mouths.
All in all, definitely an improvement on the first Thor film, and a worthy successor to The Avengers. I'd probably put it a notch above Iron Man 3, which also came out not too long ago. Oh, and be sure to stay all the way to the very end of the credits. There's a double helping of shawarma.