I first talked to the person who recruited me one on one, then talked to 3 groups of 3 members of the team I was applying for at a time. The interview was very long (over three hours I believe) but everyone I talked to was very personable. They will "good cop, bad cop" you a little bit - they'll have a group talk to you who is very friendly and easygoing, and then a group/person will grill you a little more and have more challenging questions. Don't be intimidated, it is a great easygoing place to work and everyone is friendly once you are hired. I don't remember any tricky questions, but lots of discussion and remember to have questions ready for them about what they do and how you would factor into their team.