Funnily enough, one of my main problems at first was that they did the opposite to Gandalf in the opening scene: in the book, he's strict gravitas personified, but in the movie he's genially chuckling over a line he said seriously in the books.

Granted, he was pretty much spot on for pretty much the rest of the movie, in no small part because of how brilliant Ian McKellen was and is.

I thought Legolas was portrayed as too sympathetic compared to the books, though. His haughty attitude and general jerkness towards the also very proud Gimli was a big part of what fleshed out Gimli as a character.

Making Legolas one of the biggest Marty Stus outside of fan fiction in turn relegated Gimli to almost only a comic relief parody.