I have read "The Hobbit" and "The Lord of the Rings" trilogy probably 150 times since discovering them in grade school (I was a voracious reader!) and thought that Peter Jackson did an awesome job with the movies. There is no way you could capture the entire story line with all the intricacies without some changes. And yes, Sam was rather tough on Gollum in the books (which I am currently rereading) but maybe not as bad as the movie. The reason I like to read them over and over is because there is so much detail!
Most of the time, I won't even go see a movie made from a book because I have my own visions of what the characters and scenery looks like.