I think there are two different itineraries for interview days. For me, I showed up at 11:15AM and satfor a bit in a little room with coffee, tea, water, and cookies with the other people interviewing that day (five in total) - UNC has a room designated just for interviewees to wait.
We chatted for a while, and then Axalla Hoole, the director of the med school, came in and gave a brief speech about how great UNC is and about the many opportunities we would have. It wasn't a canned speech, though, he was very soft-spoken and kindly.
Then, some current students came to take us on a tour of the med school facilities. The students were super nice, and the facilities were beautiful. We walked around for a while, chatting with them about what they thought of UNC, then went back to where we'd started for lunch (they had gotten sandwiches from a local restaurant for us).
After lunch, we sat back in the little waiting room until either a professor who would interview us came to get us or one of the office staff came to tell us where to go (if the prof's office was in another building, for instance). After the first interview we would go back to the waiting room and wait for another prof. Most people had one interview, then the next right after lunch, but I know they technically have three interview slots in the afternoon (1:30, 2:30, 3:30), so I had mine at 1:30 and 2:30 and was done, but at least one kid had his at 2:30 and 3:30.
The interviews were both with profs, only one of which is actually present when the admissions committee that dicusses applications, I believe. Both were pretty laid back. I felt very comfortable the whole time, everyone was super, super nice (profs, students, office staff, students we passed along the tour), and the interviews were very low pressure.
The whole time we were in the waiting room, current UNC students would come in to get cookies, and we got to ask them questions, too. All the students were very very nice and seemed to love Carolina.