Applied online after getting a reference. Got an email for a phone screening within 2 days. Talked to a rep out of NY for a few minutes. You must know their business model very well at all stages of the interview process. Initial rep did not ask me any questions about myself but about how I would do in a hypothetical position. After a few days, got another email to talk to two people from their Austin office on the phone for 30 m. They asked me about myself, told me their background, asked general interview questions and further quizzed me on the business model.
Got approved for the next interview stage, completed a case study in 2 days, sent it in. Then got called into their Austin office finally and interviewed/briefed with 6 additional people. My interviews went well, they were the same general questions about why I wanted to be here, tell me about your professional background, what does GLG do, etc. My case study debriefing went really well. As with all case studies, they are looking for your reasoning and not your specific answers. They asked a couple of tricky questions (rank these experts in their relevance to the project, now make an argument for the least important person being the most important).
Two of the people interviewing me seemed very busy and were checking their phones, one asked the same question two times. I caught them after a busy week so I didn't really mind but it was hard to scope their reactions because they seemed preoccupied. Based on the reactions of the interviewers and the exhaustive process, I had a really good feeling I would get the job but sadly did not.