I loved the framed narrative. I was expecting it since we knew Ian Holm and Elijah Wood were in the cast, but they did it so magnificently. I love how it ties into The Lord of the Rings movies and the beginning of those where Ian Holm does the 'Concerning Hobbits' narration. Perfect, absolutely set the right tone.
I loved the history of Erebor and seeing the Lonely Mountain and Dale in their prime. The way they cut the arrival of Smaug was teaser-ific (in a good way). Except Thorin and Balin were supposed to be away from the Lonely Mountain when Smaug came, and they witness it from afar. Also, Thrain and Thror are supposed to escape from the secret door and be the only survivors. I'm not sure what they gained by changing that.
I loved most of the Unexpected Party, especially the dishes scene. Except it was supposed to start at tea-time, which I'm pretty sure is the afternoon, not the evening. I also missed the colored hoods which are very clearly and explicitly mentioned in the book. Also, I wanted to see them playing their instruments. I'll concede that all of those are pretty minor in the big scheme of things - but I wanted to see them all in the different colors!
I loved the trolls - they captured their personalities perfectly. Except that they completely changed everything else. It was supposed to be raining, they were supposed to be having a hard time lighting a fire and they all see the trolls' fire from afar and send Bilbo to investigate instead of their ponies being stolen. Bilbo gets captured when trying to steal a troll's wallet. The dwarves then go one at a time and get captured instead of all of them fighting until the trolls threaten to kill Bilbo. And it was Gandalf who confused the trolls until they turned to stone. I'll concede that a talking wallet (as described in the book) would have been silly. Also, since the book has been broken up into several movies, they had to start developing Bilbo's character as a quick-thinker earlier by having him delay the trolls.
I loved the council scenes in Rivendell. They're touched on in The Lord of the Rings, and I think they did them well. Except for everything else. I disliked the whole Azog storyline - he was killed by Dain well before the events of the movie. The dwarves and Bilbo were supposed to enter Rivendell peacefully and by choice, and where were the singing elves? I wanted to hear their songs! And then there was the whole mistrust thing - I know there's little love between dwarves and elves, but they added Thranduil to the flashback and then made Thorin despise all elves - totally different from the book. I'm sure it will come into play again in the following movies when the dwarves are captured by the elves in Mirkwood too. And then they leave secretly, without Gandalf or their ponies?
I loved the Great Goblin. They did a good job fleshing out that character a bit (literally) and even included some of the singing stuff I'm about to gripe about. Also, the battle scene was fantastic, if a little over-the-top. It takes a lot of creative license, but it's fun at least. Except the stone giants were a bit much. It would be fine to include them, but the whole 'getting caught on the giants' knees' part didn't do it for me. Neither did the change of the 'front porch' scene, with Bilbo trying to leave and then the floor opening up instead of there being a crack in the wall. And they took out the goblins' fun little evil songs. I'll concede that Gandalf not being there at first worked out in the end in this regard.
I loved the Riddles in the Dark - they nailed this in spirit if not in complete accuracy. But no real complaints on that... Except for how Bilbo got there, and how he found the Ring. They have a flashback scene in The Lord of the Rings that shows this, and it's quite different in the new movie. Bilbo shouldn't see Gollum until he gets to the lake (really he's not supposed to see much of anything except the darkness) or see him kill the goblin (although in the book it's mentioned that Gollum had recently eaten one). Then for the escape he should lose his buttons on the door, not on some crack in the rock. And Bilbo shouldn't see the dwarves and Gandalf escape, they're supposed to have quite the head start, since Bilbo is supposed to have been knocked out for a while. I'll concede that the buttons are a minor detail and at least he lost them.
I couldn't stand the tree scene. It's supposed to take place in a glade with a wide open meeting area. Obviously Azog isn't supposed to be there. They're all supposed to get in the trees before the wargs even arrive. And then there was the silly and contrived 'trees falling into one another while the dwarves jump from tree to tree.' I'm sorry, but I don't see a pack of wolves uprooting trees like it's nothing. And then there's the battle scene with Thorin and Azog where Bilbo saves his life but he still is maybe dead and then they're all falling off the tree over the cliff only to be rescued by the eagles. And where were their aeries and why didn't we hear them talk? Smaug has a voice actor, so obviously they're making some creatures that talk. At least there were still eagles.
Other things I loved: Radagast in his entirety, Dol Guldur and the references to the Witch King of Angmar, the score by Howard Shore, and the sneak peek of Smaug.
I think in general they made it a lot more serious than the book. Which makes sense since it's a children's book and that wouldn't have worked nearly as well as a movie. But the part of me that really loves the book wishes they had kept it a bit more innocent.
All in all, I enjoyed it. If they had not included Azog it would have been a more manageable length and I think I would have liked it more. I will still be seeing the sequels and buying the extended editions and all that though, make no doubt about it.