Congrats on your interview! I interviewed at UPitt a couple months ago and my experience was a bit different than the posters above. I too heard that UPitt's interview SHOULD be very relaxed and not too difficult (by a friend who is a D1 at Pitt). However, Pitt's interview was the most "difficult" out of all the interviews I had. But it looks like my case/experience was not the norm for UPitt. I'm thinking that it most likely comes down to who your interviewer is (possibly the luck of the draw).
As soon as the one-on-one interview started, I noticed that the interviewer brought in a legal pad with a list of numbered questions/notes all the way down the page! (And believe it or not, I think he went through each one as he often referred back to his list).
My interviewer was a much older person compared to the average interviewer. For some reason, he had some strong gripe about me being an out-of-stater and kept bringing up the unlikelihood of me staying in PA to practice after graduation. I found this to be odd because I knew so many people who are at UPITT that are out of state.
One example question was: If you went to a bookstore, what section would you go to and why?
But regardless of my actual interview experience, I liked the school and the "vibe" I received from the students, administration, and facilities. They seem to have a very strong program and continuously headed in the right direction as they are constantly undergoing renovations. If I had not gotten into my top choice, I would have strongly considered UPitt as an alternative (granted I gain acceptance).
Hope these brief comments help! Good Luck.