I read up on Duke in order to answer the "why duke" question, studentdoctor net, re-read my secondary, made sure I could articulate my motivations for wanting to study medicine.
Duke med students were very happy, neat people. Campus and facilities are state-of-the-art. In general, people were very friendly and made an effort to put the interviewing students at ease.
What impressed you negatively?
the lunch...not very good.
What did you wish you had known ahead of time?
This was parents weekend. This made it difficult to find a hotel room close to campus. I suggest that you plan your interview data around hotel availability.