exmike,
i had an interview last week in dc and i wanted to make sure i told them how interested i was in their program, since the school is my top choice. after both student and faculty interviews, the interviewers asked me if there was anything else i'd like to add. that's when i jumped in, and told them how i ranked this institution as my number one choice, and if given an acceptance, i would be extremely honored and gladly accept the offer. remember though, you have to tell them WHY. i listed a bunch of factors to give legitimacy to what i was saying. i even went further and told them that if accepted, i would without any hesitation withdraw my applications to other schools i applied to. after hearing me speak about this, both interviewers said how glad they were in hearing this. hope this helps. oh yeah, i still haven't heard back from the school but i'm crossing my fingers. best of luck to you and kindest regards.