The interview is very relaxed. The Dean mentioned early in the day that you were offered an interview because you met the basic requirements, and the interview was more about them getting to know you and your motivations as well as you getting acquainted with the program. Essentially, making sure both parties agree that you are a good fit. The interview itself takes about 40 minutes and it's a small handful of questions. More like a conversation than a "grilling" interview. No behavioral or trick questions (see the link below for the interview page on this site which ended up being very true to form where questions are concerned).
Beyond the actual interview the whole experience (for me) was fantastic. You show up and meeting in a large conference room with other interviewees. 3/4 of which were for the Osteopathic program and 1/4 where for Optometry. After a brief intro from the school, the Osteopathic interviewees went off somewhere (tour maybe) and the Optometry group was left. At that point they had two groups of interviewers come in and take us one at a time. the 15 or so of us spent that time just getting to know each other and talking about our experiences, which was very nice. We also did a tour of the campus/facilities and had lunch with faculty/current Optometry students. We started at 8 and ended around 2:30.
best of luck!
http://studentdoctor.net/schools/school/azcopt/survey/26