I really enjoyed it. I saw it in 3D, and while I didn't ask I think the theater I went to was showing it in 24 FPS, because I didn't notice anything different about the picture or the way the characters moved. Simply a gorgeous film, though. While the movie probably didn't need to be filmed in 3D it was pretty neat to see the added depth and texture it gave to Middle-earth.
Martin Freeman was excellent as Bilbo. I thought he did a terrific job of taking Bilbo from his initial reluctance to wholeheartedly joining the adventure, then struggling with his self-doubt and eventually finding his courage. I really liked Richard Armitage's Thorin, too. I enjoyed the development of his relationship with Bilbo.
Radagast was pretty fun. I'm not very familiar with Sylvester McCoy, but he did a good job. I wasn't expecting the character to be quite that goofy, but it was fine. Makes me wonder how he'd have done as Bilbo in LOTR if Ian Holm hadn't accepted the part. And Ian McKellen was excellent as Gandalf, of course. I actually enjoyed all of the Dwarves, though I think Bombur was the only one who didn't have any lines at all. Bifur didn't, either, but that's because he can't speak.
I haven't read the book in years, so of course I don't remember all of the details anymore, but I liked just about all of the additions they made to the story. It was cool to see some background on the War of the Dwarves and Orcs, and to see how Thorin earned his Oakenshield moniker. I didn't mind the expansion of Azog's role and his enmity towards the Line of Dúrin; I thought it gave the story some added weight, and added something to Thorin's arc. There's no real antagonist throughout the story in the book, only the foreboding presence of Smaug (and now the Necromancer/Sauron), so for me it made sense to include a villain character who had a physical presence and gave the characters a genuine threat to worry about from the beginning.
It was a treat to see Andy Serkis' Gollum again, and he and Freeman were fantastic together during the Riddles in the Dark scene. That's where Gollum's part in the story ends in the book, but it wouldn't surprise me if Jackson has him show up again in either of the next two movies. I hope not, though. There were enough callbacks to LOTR in this movie; I think it's time to let the next two stand alone.
Overall, I thought it was great. I did think the movie took a little while to get going, but once it did I enjoyed the ride immensely.