SDN website (very good source!), school website, and read everything they sent me.
What was the most difficult question?
It is hard to say that the only question asked was really difficult. However, I think that it was difficult in the sense that the interviewer left it open ended to let you say whatever you wanted. This can be both good and bad, depending on your personality and ability to creative logical answers to this type of question.
The positive remarks from the current students. I talked to many of them during our lunch together and while I was waiting in the lobby. All of the students were happy to be there and with the training they were receiving. They made it obvious that the school was in a bad neighborhood, but they didn't let that affect their desire to be a dentist.
What impressed you negatively?
The neighborhood of course was not in the nicest area of town.
What did you wish you had known ahead of time?
How relaxed the interview would be. It was much more like a round table discussion where th interviewer just wanted to listen to you describe yourself