I, like most people, get my arms up in the air when stuff from source material is changed, especially if it's purely cosmetic (I'm looking at you David Yates... spells have different color. They're not all just jets of white light). But sometimes, changes from source material can better benefit film, or the universe in general.
I'm not sure how many people agree, but one big one for me is that I actually like how Spiderman has organic web shooters in the Raimi trilogy. I know they've tried to explain it and give reasons, but when it gets down to it, I just don't buy that a high school student would be able to create something like that himself. Maybe it's just because I was never particularly adept at chemistry, who knows. But I thought that him having natural web shooters was a great change that made it much more believable.
What are some other diverges from source material that you think made for a better change?