I've watched it twice in the theater. 1st time 3d in a big theater, 2nd time at out local cheap theater.
I don't mind them inventing a she-elf for a female lead in the story. If you can get past that, or haven't read the book, then you should enjoy this film. There's no singing like the first one, and the action is more throughout.
All of the story points with ratagast and the necromancer have been created from the index's and appendixes from LotR. Since their in cannon and help explain the story, I think its good to have them included in the movie.
I thought the spiders would have had a bigger part in the movie. The barrel ride is epic; and the reason that I went back to see it again. I liked the progression of this film. Lake town was done well. The dragon is awesome too, although their interaction with him is different. I don't know if they'll show him going to destroy the secret door, or if he's going straight to lake town.
I can't wait for the third part. The battle of five armies should be epic if it's anything like the other fight scenes in the series.
If you haven't read the book, then don't bitch about spoilers. You've had plenty of time to read it. It's a small book.