I'm a huge fan of the books and think they have done a good job on the first two movies. Here's what I think of the third one.
They pulled out all the stops on this one. 3 and a half hours flew right by. The emotional impact of this film is something far beyond what I expected it to be. In this way it truely grasped the essence of what the book was.
As a true fan of the books themselves, I could nit-pick on the details that were left out of this film. I won't. As it stands at 205 minutes, I think it has been cut down as best as it possibly could be. Sure there were things they left out, but yet they still managed to capture the heart of what Tolkien wanted his audience to experience. Well done.
The effects in this movie were at least as spectacular, if not more so than the previous two. Yet they do not detract from the story, and the viewer hardly notices them. The battle scenes are intense and very well done.
Bottom line- go see this movie. See it three times. Take your friends. It captures the essence of the human spirit.