JohnnyExtra is pretty much correct. As interviewers we're instructed to make comments to justify ratings. Those involved with the adcom have said bluntly that there are students at Drexel whose acceptance was swayed by the student interview. Also, there are students who did not get accepted due to the student interview. The impression I have gotten is that the student interview typically corresponds with the faculty interview. However, there may be instances where the faculty interviewer wasn't greatly impressed, but the student interviewer was, and vice versa. Or, the faculty interviewer had a good review, but the student interviewer got to witness "another side" of the applicant that was not good.
With all interviews, use common sense. Try to relax, but be professional in ALL your interactions.
The application process is stressful. I don't think there's anyone who comes away thinking that the whole system works like a well-oil machine or that it even makes any sense what-so-ever. But, when you attend your first day of medical school, you'll begrudgingly admit that it was worth it.
As always, best of luck!