as a movie, it was SUPERB! peter jackson is an amazing director who has the sense for visuals and eyecandy.
as a movie adaptation of the book, it was decent. one of the major changes that fans will get uproarious about [kinda like how the ending was totally changed in FOTR], is the change of the character of Faramir. He was like a boromir clone up until the point he prevailed against temptation.
and there's a lot of disliking the osgiliath scene, which was new and unnecessary [i thought it was fine].
however, this isn't a literal book adaptation, and was never meant to be. it was proposed to be the interpretation from the eyes of peter jackson. i think tolkiens descriptive provides for a lot of imagery in the book, and jackson succeeds on this part most excellently.
the plot changes and additions [elves in helms deep, aragorn's fall, the ents initial decision, osgiliath, warg riders, etc...] shouldn't deter you from seeing an excellent movie.
i haven't seen many movies that have been as good as the book (perhaps the only one was "a clockwork orange", and even that was bastardized) but this one remains close enough to the book to satisfy this tolkienite.
i still don't like arwen but she's not as cheesy in this movie.
