I am extremely sorry IIMblacki07 and gvc84, for not having posted my interview experience for such a long time. Was on a short vacation.
I had mine with Brian on 29th December. Brian is an extremely polite person and a patient listener. He started off by saying few things about UIUC MBA and then later told about what info he seeks from each candidate(the same, why MBA, why UIUC, Goals and more dope on your career progression). So I spoke for 45 minutes, uninterrupted about these 4 aspects of the application and there were not many counter-questions, during the course of my monologue.
Later, he asked very generic case and I was a tad puzzled by the vagueness of the case and probed him for some specific information before, i can analyze and suggest any recommendations. Don't worry, it's simple stuff and there is no right/wrong answer. Just the thought process is what matters the most
The entire interview lasted for around 70 odd minutes and all I can say is its not formulaic. It can revolve around multitude of topics, depending on your experience. So try to enjoy the conversation and you will do well.
BTW, gvc04 or anyone else has received the final admission decision?