Desolation is very much meh. I have literally never in my life been in a movie that felt so long. Not even midway through I swore, honest to God, that I'd been there for four hours. Lots of choppy editing back and forth when you have the characters split up (again) hurts even more, because what tension or momentum you may have established dissipates almost immediately. The CGI was jarringly inconsistent, often looking very unfinished. It'd be hard for this to be overstated. The newly over the top effects in the Gandalf scenes look they're from a video game, not that I found what was happening in some of those scenes particularly compelling, anyway. In fact, there was very little in the movie that was compelling at all. Maybe part of the problem here is that I have the Rings trilogy in the back of my head, by I couldn't stop thinking "everything here, those movies did better." Any sense of peril or fear or tension, investment in the characters and the story, the action, the effects, the score, the repetitive nature of some of the events (the company being captured, for one)... little of it is nearly as good.
That said, I don't think I'd call it a bad film, or even necessarily a boring one. I do like all the characters. The principal cast is all good, and Smaug stands out well enough. The distinction between Mirkwood elves and their kin is appreciated, and seeing those elves kick ass is always fun. The barrel scene in particular might be the most fun, well choreographed and orchestrated action scene in all of the movies, adjusted for the tone of the film it appears in. I love Manu Bennett, so Azog is always a pleasure to have on-screen, and the orcs in general aren't as odd-looking in this as they were in the last movie. I find Luke Evans to have terrific screen presence, but that might just be because he's so damn handsome.
I'll happily go see the third next year, but my expectations will be very much tempered.