I did on-campus recruiting at my university, and there were 2 rounds of interviews, with 2 case interviews each. I found the Bain cases to be a bit more straightforward than the cases for BCG and other top consulting firms. They weren't about banks, pharmaceutical companies, or companies in other complex industries that most undergrads don't have a strong background in. Instead, they were analytical problems about corporations most people intuitively understand (grocery chain strategy, airline considering adding an economy-plus program, that sort of thing). Obviously I only had four data points from my cases, but my friends had similar experiences, and the internship interviews this year seemed to go the same way for people I knew. I think the flipside of the easier questions was that they expected a higher standard of performance from people because the ceiling of the test was lower and the scenarios weren't hard to understand conceptually. It seemed like they gave us cases that feel manageable to try to put us at ease, but they didn't accept a lot of the candidates I knew who felt they had made small errors or had given solid but unremarkable performances. The interviewers seemed happiest when I went into depth and tried creative answers during the brainstorming parts of the cases, so I think they might be looking for particularly well-considered answers to cases that seem simple on face.
I also think my interviewers cared about presentation and personality based on what they said about the cases after I got my offer. They want people who are high-energy (VERY peppy and friendly -- this was a unifying characteristic for the people I met at the firm, and my friends who work there have confirmed that it's emphasized in the corporate culture) and would be good at giving a client presentation. Have a big Starbucks before your final round if you're a laid-back personality type, and don't let nerves or number-crunching get in the way of having a clear conversation with your interviewer. Long story short, the Bain cases weren't so tough, but to get the job you'll need to distinguish yourself with some innovative ideas and a great demeanor.