There are three rounds of interviews. The first is a simple behavior interview conducted over the phone. The second round is another phone interview, with two parts--another behavior interview, and a "logic" question. There are no case studies in any rounds--the brain teasers instead simulate the type of thinking process necessary in the consulting realm. The questions are not overly difficult, but as they do not relate to business problems, it can be hard to prepare for them, and they may not actually give you a chance to display your true skill. The final interview is held at their HQ, where you have a 4 hour interview consisting first of a Wonderlic test, followed by several one on one interviews which mix behavioral interviews with more brain teasers. Overall, the interviews are not too tough, although I did not get an offer, so perhaps I am underestimating the toughness. You just have to hope the brain teaser is one you can understand easily. Also, it may take some time for them to get back to you about whether or not you will get an offer. If you do really well, you will likely hear back immediately. Otherwise, it may take upwards of a month or longer before you hear for sure whether or not you get an offer, or if they will decline your application.