I completely second xzeppelin's interview experience and what he mentions regarding the interview process.
I had my interview via Skype. Unfortunately for me it was only for 30 minutes. There was only one basic question. Tell me about yourself in a chronological manner. Anything that you want to cover is fair game. So I spoke a bit about my family, schooling, college & work and how each one had impacted my personality. I was running short of time and that's why we could only devote about 5-7 minutes for the Why MBA & Why Darden questions. That was followed by 2-3 minutes of me asking some questions. Overall the interview was very conversational. There was no cross-questioning and none of Why this or Why that stuff...
Keep a photo ID handy. The interviewer will check your photo ID right at the beginning. This is mentioned quite clearly in the mail that Darden sends but thought of pointing it out nevertheless.
Bottomline - Keep your story ready - cradle to interview chair. And be prepared to tailor it based on the time. You could be asked for a 15 minute monologue or a 45 minute monologue. I had a tough time incorporating all elements of my story within the time limit.
The interviewer said that the process they normally follow is like this-
1. Two reviewers read your file and if both of them give their consent, the applicant is invited for interview.
2. A third reviewer, who hasn't read your file interviews you and after the interview proceeds to read your file. (The interviewer will continuously take notes during the interview for this reason, be prepared to be talking to his / her hair while he / she is busy taking notes)
3. Based on the interview and the third reviewer's assessment of the file, the file will be finally handed over to the Director of admissions.
4. The Director will finally take into account all the three reviewer's assessments before passing a final judgement on the application.
I think I covered it all. Let me know if any questions!