Dementors breed!!?? I didn't get THAT out of the movie! And the movie deviates even more from the book than previous movies. But, for this book, I like some of the action sequences and the ending better!
Again, I wonder how much JK Rowling participated in the screenwriting.
Even so, as in every book I've read that was subsequently made a movie, a great deal is explained as character's thoughts and emotions are described in the text. Motives are not always evident to the viewer in a film scene but the author informs the reader.