First off, I really can't see nearly everyone who worked on LotR being huge Tolkien fans, one would think they would have swayed it closer to the books.
Dear Lord, please don't let MM or joxy find this post.
Many of the changes
were unnecessary! Period. There is no denying it. You want a big example?
Theoden. Give me one good reason why they changed his character to a manic-depressive old man, so willing to abandon Aragorn at every chance? Why? There simply is none.
Ahem, pardon the rant. Also, please don't mistake my true allegiance. I am a die-hard movie fan, but I admit there are changes, quite a few to the detriment of the films.
You can see my argument agreeing with the substitution of Arwen above.
Welcome to the Forums!