Without giving too much away... story wise, it's a bit more humorous in comparison to the original trilogy. For example, comically Bilbo's quiet solo dinner is interrupted by uninvited dinner guests that come through his door one by one (or one case at the same time) that promptly help themselves to his store room and dinning room. At the same time Bilbo is trying to trying to maintain order, his dollies and mother's dishware...rather in vain attempts. A few links are made with the original trilogy. At the start of the movie, it is an older Bilbo Baggins (played by Ian Holm) narrating and writing down his adventures and contemplating how he himself has changed from that adventure just before the big party at the beginning of Fellowship of the Ring. Frodo (played by Elijah Woods) is seen wondering what his Uncle is up to. Rivendell is revisited in all it glory when the party needs to seek council with Elrod, Galadriel, and Sarumen. It is interesting to note during this scene the onset of Sarumen's downfall is seen as he believes that great power will overcome to odds, and stubbornly refuses to believe that trouble is on the horizon...or it could be he knows trouble is on the horizon but tries to confuse everyone but not believing that facts.
The theme of home vs being outside of your home is a strong theme. When see young Bilbo he is a bit too comfy with where he is right now and with his peaceful, homely life in the Shire..so comfortable its a boring life for a hobbit that used to in his earlier days wanted to go out into the world, as Gandalf would point out. So when offered the chance at first he is terrified of the dangers ahead (especially of the dragon) but the next morning he rushes to the dwarf company to go on an adventure despite not knowing what to do yet he still wants to fulfill the adventurous wishes he had in his youth. As outlined in a conversation between Bilbo and Bofur over the subject of home....the Dwarves are so intent on retaking the Lonely Mountains because they want to have a place to call home like Bilbo. They have been on the road so much and too long...they want to have place where they are not strangers. This conversion is what makes Bilbo stay on this journey...he has a home to come home to but he feels its his duty to make sure his friends have a home to.
Visuals as all is incredibly rich....we got the wide angle lens of New Zealand as the company travels. The new places visited are gorgeous or mind boggling to look at, for example the city of Dale seem to have hints of the Italian Renaissance or Tuscany with its red tile roofs; the rustic, sun soaked and yellow buildings and balconies and windows that herald a Romeo and Juliet stage production. As for the Dragon Smaug...it is nice of the film makers not to show Smaug himself in full body to heighten the tension and to show this is a really big and nasty dragon. His coming is herald with only a shot of a child's kite of a red dragon blowing fiercely in a brewing wind storm.When he launches the first attack and is storming the royal treasury, Smaug is moving too fast to be seen clearly, we are seeing the attack from his POV and is covered with flames, debris and smoke (or gold when he dives into the treasury) with only some part of his body (his eye, claws or tail) visible.
As a final thought despite being almost 3 hours long again.....it was very much worth watching. Here's the official trailer from Warner Brothers if you are not convinced.