My first interview was an hour after the morning orientation session. My second interview was at 3:30 PM. They both lasted about 1.5 hours and took place in the interviewer's offices. I showed up early for both and they seemed to be happy that I did. I had a lot of free time between the interviews to explore the campus on my own.
Both interviewers were very friendly. Any feelings of nervousness went away immediately after I met them. Both interviewers seemed to know a lot about me (they studied my application well). They have your complete application minus your grades and MCAT scores. We talked a lot about the research and clincal experiences I have had. They were also very interested in my support system outside of school (family and friends) as well as my extracurricular activities (sports, hobbies, etc).
Overall, my experience did not feel like formal interviews at all. They were very conversational in nature. It was a very positive experience.