The thing is, it's a got a rich universe out of which to mine stories; there's a reason Tolkien spawned two decades of imitators. This movie is also GOOD fanfic in places. Basically, I forgave Peter Jackson because of the elves. For those of you going "Wait, what? There are basically no elves in The Hobbit!" Yeah, I know.
Leave aside the entire Legolas-as-Spiderman schtick, which is just silly in places. Leave aside the awful cliche bit of "you think your enemy is dead but no he's just playing possum to get you" - that entire sequence could have been cut and the movie would have been stronger for it. What you have is a story of a bunch of dwarves with a mountain full of gold and a whole lot of people who want various bits or all of it. A classic trope of fanfic is to ask "What if" questions set in the target universe. What if Spock and Kirk were lovers? What if the Enterprise fell through a wormhole and encountered a Death Star? Etc. This movie is one giant set of "what if"s set in Tolkein's universe. And Jackson does best when he mines that universe for its elves.
Tolkein's elves are not just humans with pointy ears. They're people with a wholly different set of views and a way of looking at the world because they are effectively immortal. You get some of this in Lord of the Rings and a lot more in The Silmarillion, both of which get mined for this movie.
Thranduil (Lee Pace), who came off as little more than an imperious fop in the previous movie, really shines here. He shows us what elves make of honor, how caste-driven and hierarchical they can be, and how they are both willing to make alliances and yet aware of the impermanence of everyone else they interact with. His final instructions to Legolas show how elves think in terms of decades, planning for futures that might come to pass. The fact that he gets decent combat scenes on-screen and yet his most important fight happens without us seeing it is a disappointment.
Galadriel's big scene - blowing up the Ring Wraiths - is more or less straight out of LotR. In that story there's a moment where Frodo asks her why she doesn't use the Ring she wears, one of the three given to the Elves. He's clearly smitten with her beauty and argues that she'd be a fine ruler if she'd just wield the power. She responds by explaining how she'd not only be beautiful, but terrifying as well - she clearly understands that using the Ring has consequences. In this battle scene, Jackson has taken that notion and visualized it. Blanchett's beautiful appearance is twisted and distorted by the power she uses. To defeat her enemies, Galadriel must become more like them. Where Gandalf and Saruman are Maiar, essentially lesser angels who were born to use these sorts of powers, Galadriel is not and it shows. The fact that this entire sequence has jack-all nothing to do with The Hobbit doesn't matter. It's true to the mythology and it's a very good "What if..." Galadriel really did use her Ring?
Tauriel more or less steals the movie - which is just fine with me. Her face-off with Thranduil is fantastic. Her tragic love story is lifted in large part from ideas in the Silmarillion, and Evangeline Lilly completely sells it. She ought to get a Best Supporting for this performance as well as better billing - what idiot listed her below all the dwarves who get basically no dialog or important action? I flat-out bawled when she begged Thranduil to take her pain away - her interactions with Thranduil are the most Tolkein-esque things in this entire movie.
The other noteworthy performance is Richard Armitage as Thorin. His character goes through wild gyrations of emotion and he manages to portray a lot despite a limp script and some terrible action sequences that - as noted above - could have been dispensed with. In the final fight with Azog there's a moment where you can clearly see Thorin confronting his inevitable death and choosing how he's going to die. Armitage carries this off purely by facial expression and bodily action and you (the viewer) KNOW what he's going to do just before he does it. Really fine acting and props to the director for how that part is shot.
Conversely, I really did not like the mini-climax scene where Thorin is about to be consumed by his madness and realizes what's happening to him. I found it tortured and overdone, with too many mixed metaphors. The scene that follows, where he reappears before the Company in his plain adventuring garb, is far more powerful in large part due to how Armitage handles it.
OK, so there were these battle scenes. Lots of them, mostly boring. I thought the large creatures were well-done, but ridiculously flimsy. Something big enough to bash down a wall ought not to fall to a single arrow, no matter how well-placed. In gaming there's a term "bullet sponge" to describe mobs that seem to take forever to fall down despite many hits and I can understand wanting to avoid that, but this movie goes too far overboard in the other direction.
I absolutely refuse to touch on the utterly stupid idea that people in light or no armor are going to overmatch heavily armored troops. Why the dwarves sallied without any armor when they had the finest armor available is hair-pullingly dumb. But then again, so is most of the "plot" here so picking on just one bit seems too easy.
3/5 for being able to pull off a story that has almost nothing to do with its titular book and yet showed us something interesting.