[Darby]

My opinions... I think movie-Boromir totally changed my outlook on the character. I hated the book-Boromir! I thought he was a big dumb thug and was happy to see him die. Sean Bean's Boromir was sympathetic and tragic. Big improvement!
Movie-Frodo? Probably my least favorite change. He looks good, but he lacks the quiet bravery and thoughtful intelligence that book-Frodo had. Book Frodo was scared but brave! He fought off the barrow-wights, deliberately risking his life to save his friends when he could have simply put on the ring and escaped all by himself. And he tried to face down the Riders at the ford despite being morally wounded. I *hated* the whole Arwen wailing over Frodo scene.
Oh, and Arwen... Actually she's mostly ok, except when she's over-acting. I understand the desire to replace Glorfindel and give her a bigger part. I can see why Aragorn would love her.
Aragorn? He looks wonderful! Just as I imagined (except maybe a little on the youngish side). But his character is too self assured. I absolutely adore movie-Aragorn, but book-Aragorn is a little more wounded by experience. His face is "drawn with pain" when he talks about the Riders to the hobbits in the inn. He says something sort of wistful about wishing they'd accept him on his own merits. You get the impression in Bree that he's kind of lonely, and he blames himself when things go wrong and Boromir dies. He's a lot more self-critical in the book.
But Viggo is just scrumptious and he could be my king any day, so I don't mind the changes at all. :-)
Faramir is terrible. He was my hero as a teenager - almost Christ-like, and terribly noble and intelligent and just a little... not cynical, but he had a very quick wit. I saw him as more of a intellectual character, not so muscular, a Robin-hood type fighter as opposed to a knight or a warrior. And he was younger - especially in his relationship with his father, and the way he kept trying to hide his hurt feelings at his father's constant rejection. Having him be Boromir's mini-me is just not on. Sorry, movie-Faramir can't ever be Faramir for me.
Sam was perfect (especially when Sean Astin's doing the sort of stolidly-outraged thing); Gandalf was perfect; Merry and Pippin were fine, but too old looking; and Treebeard was not nearly wise and subtle enough. Book-Treebeard could never have been tricked like that. He knew lots and never let on to Merry and Pippen in the books, and he led them into telling him a lot more than they ever intended to.
And I was fine with all the other characters. I was very happy with the elves - best portrayal outside of the book that I've seen (the BBC's elves all had high silly voices, and the animated elves are just indescribably awful).
PJ's vision of middle earth comes closer to the way I imagined it in the book than anything else I've ever seen. I think the films are fantastic! But, they're PJ's vision, so they won't match perfectly with mine or anyone else's.