1) Acting - Unlike the cherubic, doe-eyed Elijah Wood (who was supposed to be the same age as Blibo when he started on his Fellowship), Martin Freeman does look the part, and really "becomes" his character. His performance cannot be faulted. Everyone reprising their roles from LOTR are up to par. Designing 13 Dwarves is a huge challenge, and the creative team largely succeeded in differentiating them, and giving them unique personalities. The balance between their dignity and comic relief is just right.
2) Scenes from the Book - When Jackson sticks closely to Tolkien, it works. The entire Bag-end sequence was one of the highlights of the movie for me, it didn't feel long or bloated at all - a fitting introduction. The Troll scene was delightful, and even some of background history from the Appendices was well-realized.
3) The Visuals, of course - More sweeping panoramas on New Zealand/Middle Earth, and we get to see Erebor and Dale at the height of their glory (in a flashback).
1) Riddles in the Dark - I may have simply expected too much from this scene, so it ended up a bit disappointing. The acting by Serkis and Freeman was fine, but the scene was somewhat awkwardly filmed, especially when Bilbo escapes, and the way Bilbo solved one of the key riddles was altered needlessly.
2Radagast the Brown - the subplot was not as annoying to me as many have found - it served a narrative purpose to show the transformation of Mirkwood and provided some extra cuteness. His character was eccentric enough to merit Saruman's insults, but Jar-Jar old Raddy is not.
3)The Songs - the Dwarf songs were better than much of the LOTR soundtrack, and worked well. I found their inclusion a good way to honor the text.
1) Gratuitous action - not that all of the action sequences are outright bad (yes, it's an adventure after all, and yes, there are a few nifty ideas), but they need trimming. With all the relentless cliff hopping, head chopping, and 1000 ft dropping, Jackson panders to the video-gamer audience. There were similar scenes in LOTR as well, but here, almost the entire last hour is packed with them.
2)Overused Cliches - it seems that in Jackson's universe, it's a common occurrence for characters to fall off cliffs only to reappear later. How many times must we endure? The Goblin-King's demise is case-in-point.
3) The last 10 minutes - I understand the need for an underlying arc and a proper conclusion to the first film, that's screenwriting 101. The way it's wrapped up, though, to me was the most jarring moment - on par with "Elves at Helms Deep" or "Frodo sends Sam home" for some. It's ridiculous for Bilbo to turn into an action hero at this point. He's still growing into the burglar role, and is far from a warrior. In fact, according to Tolkien, he stays away from battles (even at the end of the book) by putting on the ring! Thankfully, the scene is easy to remove without breaking up continuity when the fan-editors get their hands on the DVD.