Like Jeruba, I care more about faithfulness than completeness. The things most important to me (but not in order of importance):
1) Glorfindel should not have been replaced by Arwen.
2) Aragorn’s mom’s lines (taken from an appendix) should not have been divvied up between Arwen and Elrond. That’s just weird.
3) Faramir should have been allowed to keep his spine, which rather nicer than the spines of most Men. Peter Jackson turned Faramir into Boromir 2: All the Same Flaws And Also a Little Wimpier.
4) Denethor was pretty far off-character, too (but not as much as Faramir).
5) It would have been pretty cool if Beregond was left in the movie. He was a minor character, but he provided a glimpse of one of the “little guys” and also demonstrated how well-loved Faramir was.
6) Aragorn should have let the Dead Men of Dunharrow be free once they had fulfilled their oath by helping him defeat the corsairs. The Men who had previously been occupied with the corsairs should have then come with Aragorn rather than having the Dead Men of Dunharrow act as a deus ex machina. Leave the deux ex machina-ing to the eagles. They’ve been doing it since The Hobbit and they’re pretty good at it. (Also, since the Great Eagles are the agents of Manwë they demonstrate the involvement of the Valar, though that would not need to be stated explicitly in the movie. It isn’t stated explicitly in the book, but it’s cool once you know.)
7) Saruman’s death should not have been so different from how it was in the book. Even without including the Scouring of the Shire, Peter Jackson still could have allowed Wormtongue to betray him.
8) Gandalf should have been allowed to face the Witch King resolutely at the gate rather than fearfully in the middle of the city. The breaking of his staff was just plain stupid. He should have broken Saruman’s staff earlier simply by pronouncing, “Your power is broken,” but his staff should not have been broken by any means.
9) The dialogue between Eowyn and the Witch King should not have been cut so short and the tiny remainer mutilated. This is the single scene in the trilogy that I was most looking forward to seeing, but it was practically not even there. (”But no living man am I! You look upon a woman. Eowyn I am, Eomund’s daughter. You stand between me and my lord and kin. Begone, if you be not deathless! For living or dark undead, I will smite you, if you touch him.” > “I am no man.”) The Witch King’s actual threats were also far better-written than Peter Jackson’s, “Die now.”
10) The importance of Merry’s role in the destruction of the Witch King should have been acknowledged. Had he not struck him with an enchanted blade right before Eowyn landed her blow, then the Witch King would have remained invulnerable. Peter Jackson seemed to totally miss that. Part of the problem is that because Tom Bombadil was not in the movies the hobbits were never captured by the barrow-wights so that Merry could obtain the enchanted blade from the Barrow-downs in the first place. That said:
11) I don’t really care about Tom Bombadil’s absence from the movie. Leave him to the books. Readers are more likely to be able to handle the amount of mystery that he entails.
I believe that all of these points could have been adhered to without lengthening the movie. In fact, at least one of these points would have reduced the length of the movie because viewers’ time would not have been wasted by watching Faramir bring the hobbits to Osgiliath.