i interviewed at duke a couple weeks ago... there were only 3 people there on my day, and we were told that most of the people that had interviewed already were duke ugrads. so they;re slow, but moving along. it wasn't much to worry about, just enjoy the day. It's probably the nicest facilities, settings, surroundings you're gonna see and I really loved the school in general, good luck
(i've heard nothing from harvard either, but forget them, I'm dropping harvard, that attitude/style is not for me) 🙂