The interviewers I had were really serious MBA-type people, and no matter how hard I tried to lighten them up they just kept right at it! It consisted of one 1:1 interview and then a second-round interview the same day with 2 people. These interviews were really average, and I walked out of them thinking I botched it but apparently they liked me. So it goes. The process itself was really quick because these guys are super efficient, which I really appreciate in an employer. I found out I was hired within a week of interviewing, whereas other places made me wait 2 weeks or more.