I was invited for an interview. Everything was clearly explained - the personality questions and the case studies they have on their website correspond to what you get in the interview. You are interviewed by two people in the first round (not simultaneously). I didn't do well in the case study, but that was my fault. I didn't prepare well enough. I think you need to do more than the case studies on their website - you need to get to the point where you're familiar with the structure of a case study, so that the only new thing are the actual numbers. That's purely because you have fairly little time - they're not pushing you, but if you get a couple of minutes to figure something out, then if you bumble about a bit, you've basically ruined your chances.