So, I just saw The Hobbit: Desolation of Smaug tonight, and I'm pretty damn stoked.
Smaug, as you may have guessed, was my favorite thing in the whole movie - and I liked the movie overall, a lot! Not only does he have a really cool design, Benedict Cumberbatch does a truly great job as Smaug. He's arrogant, vain, cunning, cruel and greedy as heck. Truly, Smaug in this movie is going to be the standard against which all dragons in fantasy movies are going to be compared from now on.
The rest of the movie was very good, too. Bilbo and the dwarves were great; there are some very interesting moments with Bilbo and the Ring, in particular, and while Thorin and Balin get the most screen time, the rest of them are well handled too. Tauriel, the elf warrior woman added for the movies, fits in really well, and Evangeline Lilly manages to steal a lot of scenes. She's the best female warrior I've seen in ages!
The scenery deserves a mention. It was uniformly gorgeous, from the dark and choking Mirkwood to the underground beauty of Thranduil's halls; from the terrifying haunted ruins of Dol Guldur to the Laketown that's best described as run-down Viking Venice, clearly going through hard times yet still bustling and interesting; and to the grandeur of Erebor itself.
Overall, I rate it higher than the first Hobbit movie; the additions and changes from the book work better here, IMO, and the whole thing just seemed to click. Well worth seeing, if you like Middle-Earth, elves, dwarves, orcs and especially dragons.