I got accepted recently from the middle tier of the list. I would suggest either calling or sending Katie Horne a quick, polite email asking about the status of the list and your chances. If UMich is your first choice, be sure to send her a letter ASAP letting her know that you'll attend over any other school, if you haven't already. I think with the waitlist, what tier you're in means some but not a lot with respect to your chances.