I got to see the movie two days early thanks to a vendor that wants my business. Spoilers after the jump.
It's still a little long. One action sequence with the dwarves near the end went so long that I forgot that Legolas was in the movie, then he reappeared, continuing an earlier fight sequence. But the movie is definitely shorter than the first film, and has an ending that will leave you wanting to see the third movie immediately. I was never bored, which I couldn't say about the first movie (where I checked my watch at least three times).
There are some new plot points not necessarily directly mentioned in the book. There's a hint of romance between Kili the dwarf and Tauriel the elf (who's completely invented for this movie so who cares). Orc armies massing at Dol Guldur. Laketown politics! Stephen Fry is perfect as the Master of Laketown.
There's a really long but exciting battle between the dwarves and Smaug in Erebor that I don't remember from the book. We see more of Erebor than we did in the first movie.
There's so much Legolas. His father Thranduil is barely mentioned in the book, so there's easily 30-45 minutes of Legolas here that was invented just for this film. Benedict Cumberbatch is great as Smaug. And wow that dragon look cool. I know it's all in a computer, but Smaug rampaging through Erebor was fun as hell to watch.
Peter Jackson has a "blink and you'll miss him" cameo at the beginning of the movie and Stephen Colbert has one in Laketown. Sadly, he was not playing a mime.
The spiders in Mirkwood are scary as hell. I'm no fan of spiders but I didn't think I was squeamish about them until I was on edge for that whole sequence. Peter Jackson still knows how to make a good horror film.
It has a tremendous cliffhanger ending. The third movie should open with a hell of a fight scene that ought to take a good 20-30 minutes in Jackson time. Then we'll have an hour of the Erebor siege and more action at Dol Guldur. We'll see Dain and elves from the Iron Hills. And we'll finally get the Battle of the Five Armies which in Jackson's hand will make the Battle of the Pelennor Fields look like a Orc-Elf skirmish outside Angband. You guys know what I'm talking about. And I assume the resolution of the Dol Guldur story will happen at the same time as the Battle of the Five Armies, because that's how these things usually work. I can't wait to see Gandalf, Galadriel, Radagast, and Elrond(?) driving the Necromancer out of Dol Guldur.