As soon as I got the March waitlist email I sent a letter of continued interest, along with a letter thanking them for being hands-down the classiest admissions office. I hated to sound like an a$$-kisser, but it's the truth.
Dean Zearfoss called me on Friday to check in (I didn't report it here because I was afraid of jinxing myself.) We had a nice chat - she said she wasn't making any offers yet, but had pulled a handful of files that she was very interested in. So I sent a follow-up email yesterday and she responded with the news today.
The real irony is that I took Friday's phone call in the car, driving home from the post office after overnighting Northwestern my deposit. (By this logic, I just need to send Michigan a deposit to get a Columbia acceptance! (I'm kidding.)) I'm not complaining; I'm delighted to have this dilemma.