If you get interviewd early and don't blow it, your chances of getting in are pretty good. Depends on the school but the ones I have been following, they usually interview between 200%-400% of their class size. They assume that between 30-50% of those accepted do not eventually choose their school. So lets take a school with 100 seats, they interview 300 or so, invite 200 over several months.
Also timing is a big factor. For instance, at UoP, at this point even if you are an amazing applicant, the chances of getting in are very slim.