I was asked to expect at least 3 hours for the interviews. I Met with 4 different people for 45 minutes at a time. Spent 45 minutes with each of the interviewers (in their office) and went from one interviewer to the next. Questions were Situation Based. Tell me about a time...
How would you handle...
For the most part, the interviewers were very nice and not too intimidating.
I left the interviews feeling like I had done a pretty good job.
Piece of advice: Check out Koch's Guiding Principle's (Humility, Integrity, Compliance, etc...) and try to relate your answers to their questions to these principle's. Try not to be too obvious about it though, or they may think you were coached on what to say.