I really like the "Accept Rate" feature. I think it will encourage folks to accept answers once they get a good one (though, hopefully they will not accept bad ones just to get their rate up).
I have a concern about this though, I have several questions that no one ever posted an answer for. I also have a few that were closed before I could accept an answer.
Questions like these that are not "acceptable" should not count towards my percentage.
I also think, though on a lesser level of importance, that any question with only negatively scored answers should not count towards your accept rate. (Sometimes people throw out crap answers just hoping to get an up vote or an lucky guess.)