Had my interview on Monday. 30 mins, about 15 questions. One interviewer who led the discussion, and one observer who was mostly silent taking notes, but asked me some probing questions. Both very friendly and kind, but very formal at the same time.
Their last question was "is there anything you wish we'd asked", so I assume that we managed to go through all the questions they had prepared. It was a very intellectually stimulating conversation, and I think it went well. I enjoyed it.
The whole application process is now finished and regardless of the outcome it has been a fantastic experience.
Good luck to all applicants who are still to do their interview!
EDIT - having read the latest posts, I completely agree with Webster and GavinE. They asked me lots of probing questions to test my mental agility and, I assume, my capacity to contribute to case discussions. A few questions related to my industry, and obviously I knew the topic very well. Some other questions related to other industries, and I had to remain calm, quickly put thoughts together, and go ahead with a crispy and concise answer that I definitely had not rehearsed. I agree that it was exhilarating and not relaxing at all - but definitely a terrific experience!