The movies were pretty good, though I was disappointed that they cut out Tom Bombadil. They did stay relatively true to the tales though, and kept a good sense of right/wrong and good/evil.
In his hand he carried an ancient and trusty weapon, called by the elves a Browning semi-automatic.
Yeah, Arwen saved Frodo, not Glorfindel. While I enjoyed the movies quite a bit, I was annoyed by a number of things such as Arwen's "you want him, come and claim him". I've read the trilogy 5-6 times in the past 30 years or so and I have to roll my eyes at that one. Glorfindel sets Frodo on his horse and sends him across the ford of Bruinen thereafter invoking Elrond's invokation to have the ford wash the riders away. In the movie...Arwen does it and rides across with him.
Bombadil would be extremely difficult to adapt to the screen since he's essentially insane. An immortal with unlimited powers, as he was before and he will be after. He makes Treebeard seem like a hatchling. I can't imagine how you could do Tom without going way into some weird Monty Python type of world where you find a refuge in the middle of war where people feel that basket weaving is the most important task of the day, everything else being useless dreck.
In order to do justice to Bombadil’s pervasive influence in the history of Middle Earth, the movies would have had to be 2-3 hours longer. I was disappointed, too, until I realized how hard it would have been to create all the needed backstory of Ol’Tom that Tolkein is able to imply and to scatter through the books.
All in all, I believe that Jackson and his writers did a spectacular job of bringing this story to the public. In order to do a better job, someone will need to write a book. Oh, wait, I guess someone already has!
What really got me was leaving out the "scourging of the shire," although it was alluded to in Loth Lorien (and seen in the bounty at the sack of Eisengard), as something that might come to be. It seemed to me that was terribly important in showing that the typical Hobbit attitude (keep to yourselves, and nothing bad will happen to you) just doesn't work when confronting evil.
I always felt that this was a major point of the allegory, and leaving it out left out a major point of the tail.
Mark