I went into the movie prepared to relax and enjoy the silliness, but I still found much of it almost unwatchable. Aside from a few scenes that I enjoyed (spiders were creepy and not overly ridiculous, woods ditto, some of the acting/actors, <3 Freeman, the intro to Smaug, some of Gandalf being impressive), I mostly could not stop being annoyed with one thing before something else happened got me going again.
I never think of myself as a purist, but I couldn't handle so many stupid diversions. I almost flopped out of my seat in a temper when they "met" Beorn. I can understand why they chose to handle him that way, and I think I could've lived with it if there hadn't been so many other ridiculous things. And I'm not counting the additions - Tauriel was fine, Gandalf-on-quest was fine - because you can't ruin something that didn't exist previously. It's everything else.
Would barrels float if repeatedly dunked under water, presumably filling with water? Gimli was so awesome because he was clumsy, clunky and small, but still managed to be a badass. In some ways, these dwarves are given Elvish powers (ie: Bombur? in the twirling barrel of terror, who then jumps into an empty one), then in the next moment they are slapstick morons.
Thorin rode an apparently heat-insulated wheelbarrow down a channel of molten gold...
They blew up a massive statue of a golden dwarf king that they all somehow knew the location of, and exactly what to do to melt it on Smaug (who was then immediately brown again, and went to kill humans!) I swear to god, I'm getting angry again just thinking about it. Maybe Legolas could balance on top of a barrel-bobbing dwarf's head, but should he? Should he?
I don't mind goofy movies; hell, Ice Pirates is one of my favorite flicks. I guess I couldn't quite manage my expectations, because I could NOT get over the implausibility of damn near every action scene. And I really wanted to like them.