My first interview took place at an MBA forum in March (Chicago), with my MBA class graduating in May/June.
The first round was a 45-minute behavioral interview, followed by a brief 15-minute behavioral type chat with the MBA recruiter at the forum.
The second and third round interviews were held over the phone, and were both typical behavioral, and lasted 30-40 minutes a piece, as we ran a bit over.
The fourth and final round was a super-day held in their Chicago office, during which I chatted in person with two consultants, over the phone with two others (different offices but same group), along with a lunch and then an industry specific case. The case was not bad - it was NOT heavy on the quant side, and did not require a lot of computation.
They had to reschedule one or two of the interviews, as client engagements popped up and drew the consultants away from the interview process. While this was not ideal, they are still a smaller firm and do not have the same resources that a larger big 4 would have when it comes to staffing for recruitment type events and interviewing.