In a Lost podcast a few weeks ago, the guys said that when Kate decided not to run without Sawyer, it was meant to show that she had picked him. It just wasn't as clear as it was supposed to be I guess.

I would have stopped watching the show (maybe) if she had picked Jack, because from a character and psychological standpoint it would have made no sense. The episode showed us that she is unhappy playing house with the good guy cop (or surgeon). She might wistfully want that life, but she knows it won't work. People are generally attracted to people who have similarities to their parents (ie-Sawyer and her biological father). On top of that, Sawyer understands her a billion times better than Jack ever will, and he takes her at face value, sees all the bad things she has done, and still loves her for it. Jack has judged her the entire series.