Applied through campus recruiting for a full time position, and after a number of networking events and the resume drop, was notified that I was selected to interview. 1st round interviews were on campus. A few days before the first round interview, BCG arranged a mock case interview with a consultant which went smoothly. First round consisted of two interviews, the first one with a consultant and the second with a principal.
My first interview went fine - after relating a behavioral story, I received a case asking to diagnose why profitability was declining, and correctly identified the root cause and came up with suggestions. I was nervous and made a few errors in my math. My second interview was also a profitability case, but I was less successful, as I couldn't develop a rapport with the interviewer and grew discouraged trying to find the "right insight" to diagnose why the client had so low profit margins. I did not advance to the next round, my key feedback being that I jumped to conclusions and didn't show enough drive and excitement as I tackled the case.
In general, however, BCG's recruiting process was professional, and in contrast to the financial services industry, gave clear feedback and the recruiters were responsive and helpful.