Tiawahcowboy, we all have our opinions.
The point is, the filmmakers are under no obligation to follow the story to the letter. Few if any movie versions of books do, simply because books are books and movies are movies and the two media have different requirements. As adaptations go, I'd say this is more faithful than most. I read the story first, and my impression after seeing the movie was that it was very similar to the story.
But sure, there are characters added and details changed in Brokeback, and no doubt the filmmakers had their reasons. To
me, it doesn't make sense to criticize one in terms of the other. However, Tiawahcowboy, if you like to compare the two, or even if you want to condemn any aspects of the movie that differ from the book, that's fine and it's your business. Just don't expect everyone else to agree that differences are the same as faults.