Certainly one of things that's going to make The Desolation of Smaug fantastic is the fact that there are so many new characters to introduce, and most of them are awesome. The first set of characters are the Silvan Elves of Mirkwood. You remember the Elves in Rivendell, right? Tall, pretty, slightly lethargic, all talk with annoyingly musical tones. Well Tolkien wrote that the Silvan elves were less wise and more kickass (or something along those lines). And from the trailer we can see plenty to suggest that these elves are going to be involved in some serious fighting.
On top of that, there's the return of Orlando Bloom's Legolas. My least favourite character of the Fellowship, I'm nonetheless pant-wettingly excited about his appearance in this film. Also, whatever you think about it, Jackson's addition of the made-up girly elf Tauriel looks pretty damn cool in the trailer. As the final cherry on the cake we have Lee Pace's first real appearance as Thranduil, the King of Silvan elves (his cameo on a moose in the first film didn't really count). Between him and Legolas, we should see the best collection of eye-brow acting since Colin Farrell last graced our screens.