A great movie with some long moments... - This is one of the best movie of 2002, but you'll probably find that some things are really not what you have expected.
At the beginning, the combat between the Balrog and Gandalf is one of the best moments of the movie. You will remember this part for a long time, i'm sure of it. Frodo and Sam meet very quickly the creature Gollum in Emyn Muil, when you'll see for the first time the CGI character, you will pratically not believe it! It's amazing! Practically real with great interaction. The two personalities of Gollum are clearly defined and you will have pity for him... At the end, the battle of Helm's Deep is the greatest part. But, I will not say any details on this .
The visual of all the landscape in this movie IS Middle-earth. Sometimes dark, sometimes shiny... And look at Edoras! The new characters, Theoden, Grima and Eowyn, are almost like in the books. Oh, and Fangorn too! The fangorn forest is very well represented.
But, a very very bad mistake is Faramir. Forget this part of TTT, it's the worst part and the fidelity to the book is really not there. A great deception. Too much Arwen too I think. Some people will not agree with me, but just the flashback would be okay... Another deception that i've find is a mistake for Eomer : he's practically not in the second movie. And I don't remember that the elves join the men for the battle of Helm's Deep!!! (sorry for the spoiler )
Finally, it's a great movie, but the TTT book is not there for some important key parts. The adaptation is worse than FOTR. The scenes with Faramir at the end (with Frodo who wants to give the ring to the Nazgul ?) and the other with Merry and Pippin was an half of hour too long for me. And the end is, I think, very bad, compared to the book.
But, it's a great movie, believe me, and it will be a great hit of Christmas Vacation. I recommend it to everyone! So go on, buy your ticket!