Though I understand the criticisms, I think the version of "Differences" I read was useful, and the re-write suggestions were mainly about form. I think that there are some general principles that exist in the books that are distorted or abandoned in the film, to the detriment of the latter.
1. Deliberation. The longest chapter in the book is The Council of Elrond. Those who have arrived at Rivendell seemingly by chance go over all of the facts that are known of the Ring. At the end, after Frodo says he will take the Ring, Elrond says, "If I understand aright all that I have heard . . . ." In other words, it's not a light decision, or one he had thought all along. It was arrived at by carefully analyzing all the facts.
The other big deliberation is the Entmoot. I'm still scratching my head about this one. The ents hold the Entmoot because their nature is slow deliberation. As Treebeard explains, making a decision does not take as long as going over and clarifying all the facts. As Merry and Pippin wait, at a certain moment they become aware that the voices have stopped. There's a loud boom and a gust of wind and the ents come marching making noise of drums and trumpets and singing how they will "hew the stone and break the door." Can you get any more dramatic than that?! But Peter Jackson had a better idea. Also: Treebeard tells the hobbits that one of his motivations is giving aid to the other peoples of Middle Earth before the ents are gone. This is turned around in the film.
2. The ability to see part of what will be, aka the gift of foresight. In Tolkien, foresight is not a crystal ball you can look into when you want. While talking to Elrond about Arwen, Aragorn suddenly realizes that the time of Elrond and the other High Elves in Middle Earth is drawing to an end. When Glorfindel peers after the departing Witch King in the last battle of the North Kingdom, he is struck with the insight, "Not by the hand of man will he fall," though it should have been "Not by the hand of a man." In the film, Arwen justy asks that Elrond look into the future for her.
Galadriel's foresight is of a slightly different nature, I think. She regularly talks about what will be. But it's not a simple supernatural power. I got the feeling that it was a keen perception of the trajectory of events that led to her foresight. For example, she knew Boromir was in danger from the lure of the Ring, but did not fully foresee his fall, and then his redemption and heroic death.
3. Character and fate. Aragorn fulfills the predictions and hopes made about him. But it never seems automatic -- he's the chosen one, so of course he succeeds. Some of his boldest actions -- probing the palantir, taking the Paths of the Dead -- are bound by a combination of immediate circumstance, the need that drives him, and a larger fate. He feels that the palantir has come into his possession so he can use it to challenge Sauron, and to scope out his actions.
Hope these thoughts are interesting to someone.