I think the greatest achievement of this film was that I never once thought of Kong as a computer-generated creature. He is completely believable and, unlike previous incarnations, acts extremely ape-like. That is, all the gorilla behavior I've seen on various nature shows made Kong's actions seem realistic. I also liked the scale of Kong. He never seemed tiny but he didn't seem grotesquely over-sized either.
The trailers prepared me for the return of the dinosaurs to the storyline but nothing prepares you for the intensity of the fight between Kong and the dinosaurs. There are a few silly bits with the dinos, but I think they were handled quite well in general.
Kong in New York was also done well. The sets looked very realistic and seemed entirely true to the period. The emotional connection between Kong and Ann Darrow was reinforced well in these scenes.
The ultimate death of Kong (that's right, the boat sinks this time too) had sufficient emotional impact. We get to cheer for Kong as he battles the planes, but it's just a matter of time before they bring him down.
The theme of the film is summed up, in my mind, in the irony of the final line of the film and the character that speaks it.
It's definitely worth seeing and I think the big screen will add some enjoyment to it. Jackson's direction keeps things moving for the most part and sets up the emotional beats of the film well. You don't notice the three hours in most cases.
Nod to lsanderson: No nekkid men, but the nearly-nekkid native boys struck me as quite pretty in a lean, muscular way.