I posted the acceptance to Columbia. I received a phone call from a professor on Wednesday afternoon wanting to know if I had accepted an offer somewhere else. When I said no, she said a formal acceptance letter would be sent out later this week. I'm about 86% sure I won't be taking the offer because I was admitted to my top choice as well, but I'm planning on going down to visit some time in March. My impression is that the program is quite small - does anyone know anything about it?