Last night, after finishing Mansfield Park (the novel), I decided to watch Mansfield Park (the 1999 film, with Frances O'Connor, Johnny Lee Miller and Embeth Davidtz). I remember going to see it at the Coolidge Corner Theater when it first came out, and that critics and viewers had made an issue of the fact that the writer/director, Patricia Rozema, had taken liberties with the story, including changing the ending. At the time, I hadn't read the novel, and I don't think I've watched the film again since then (or at least not often), so it was fun to go back and look for the differences.
The Fanny Price of the movie is not the Fanny Price of the novel...she has high principles and morals, but she's much bolder, spunkier, and has more imagination. Even wimpy Edmund (not my idea of a romantic hero) is a little bit more dashing here. Sir Thomas is harsher and creepier; the page or two of explanation of why he chooses to send Fanny home to Portsmouth is replaced by dramatic anger, and the scene at the end where Fanny discovers Tom's sketchbook adds to an interesting portrayal. Mary Crawford is more one-sided, too, but it's easy to see how it's necessary to collapse characters when a novel is made into a film. (The little scene at the end where we're introduced to the Crawfords' husband and wife was a perfect invention.)
And yes, other liberties were taken with the ending, but why not? In a commentary included on the DVD, Rozema freely admits that she added elements from Jane Austen's life and letters to the story...now that I've read several biographies, those were easily recognized, which was part of the fun. And I thought the double-casting of Lindsay Duncan was inspired! It would have been fun (although difficult) to see her play Mrs. Norris as well.
All in all, I liked the differences...and somehow, I think Jane Austen would have liked them, too.