Well, I don't think you can compair the BBC miniseries and Keira's film. They'll have to leave out certain scenes to make the film a decent length, so it will never be as close an adaption as the miniseries. That's probably what all Austen fans will nag about. I loved the book, and hope Keira's film will do it justice.
Secondly, wasn't Elizabeth supposed to be less pretty than her older sister, but smarter and funnier? They're not gonna find anyone beautiful enough to play Jane then :P