The day ends about 2, and no, the interview is not stressful. Keep in mind, that the interview is "open-file", so the interviewer will have you grades, MCAT scores, etc. in front of him or her. That could be a little intimidating. What's helpful to remember is that the interviewer is your advocate: it's in your best interest to just "sell yourself" and openly explain any discrepancies (grades, etc). Hope this helps.
Joe