I don't read reviews, because reviewers are not me and thus aren't very good judges of how much I will enjoy a movie. I really like some movies/games/books that other people can't stand, and vice-versa. Anyways on to my review!
I think it tries way too hard in the beginning to link this film to the Lord of the Rings
films, somewhat assuming that you've already seen those to begin with. Birthday party? Who's Frodo? etc. I've seen the movies and I know what they were going for, but it feels somewhat inappropriate for a prequel, especially if you're a newcomer watching the movies in chronological order.
I somewhat like the more cartooony feel that comes in sometime, with the Dwarves cleaning the dishes and especially the Goblin King. For a few minutes I almost thought this film was going to be a musical, with two songs in relatively quick succession. But musicals aren't popular today, and for every song I liked there would probably be three that I hated.
Since it's impossible to write for 13 dwarves and make them all good, I think it was a good idea that they gave them all unique visual designs instead of giving everyone at least one scene. They're all fairly memorable, despite some of them not having any lines that I can remember.
Of the changes to the source material, I think the one that I like least is the White Orc. This film doesn't really need any more bad guys, and the escape from the Goblin King is a fitting end to the first half without adding another villain. I cared a lot more about the Necromancer and Mirkwood than the White Orc, supposedly the main obstacle on their journey to Erebor. They could have cut one out and fleshed out the other, but they tried to have their cake and eat it too. There was no reason for him to have been CG either, considering the excellent prosthetics they had for much less important Orcs in the LoTR
Everything else in the movie was cool. The goblins were vicious, the trolls were hilarious, Gollum was suitably crazy, the Necromancer was terrifying, and the escape with the Eagles was a pretty good point to cut off Part 1. Most of the combinations, additions and exclusions from the source material are for the better, except for the White Orc of course. B+.