I didn't really like the Radagast parts. He wsn't even supposed to be in the story. He's mentioned in the books for one paragraph and thats it.
Some people think the only reason why the film was extended into three films is because Peter Jackson is more or less a failure outside of Tolkien based films (cough cough King King - which did 'amazing' in the box office).
My favourite part was when frodo and gollum were riddling ^_^ that was my best part in the book too.
The Mountain Titans were so cool! It really surprised me. I think, visually that was my favorite part. I also like all of the scenes where Bilbo is charming (which is a lot of scenes).
Also, the part where Radagast took a hit from Gandalf's pipe. Two of my friends and I were laughing like little kids at that scene.
Personally, my favorite parts were when Bilbo read the contract and defended Thorin from the white Orc.
As for the ending, it really surprised me! I got sucked into the movie, and was wondering how they were going to approach the Forest when it suddenly ended! My dad was with me and laughed at my expression, and explained that it was indeed going to be another trilogy. Now that I look back it's hardly surprising. With the success of the previous series, why not prolong the moneymaking machine even further? It also adds to the story all the more, because even the Hobbit put in one movie would be awfully condensed. I can hardly wait for the next installment!