Disclaimer: One of the interviewers was my internal reference as well. All titles are paraphrased/alternatives
1. Initial discussion with hiring manager to gauge level of interest on both sides
2. Recruiter Phone Screen
3. Peer Technical Phone Screen (because position applied for was different from position interviewed)
4. On-site interviews
4.1 Recruiter intro/level-set
4.2 Divisional Head interview
4.3 Lunch interview with hiring manager
4.4 Sub-divisional Head interview 1
4.5 Sub-divisional Head interview 2
4.6 C-level interview (no, not Zuckerberg, but close enough :-) )
4.7 Hiring Manager interview #2 (because lunch was truncated for other reasons)
Almost 4 weeks to the dot for response. Feedback was very positive, but not a clear fit for position (I agree too).
I have over 15 years of experience working for about 10 different companies, but this interview experience will stand out in memory for a long, long time. Not a single dud interview. Each interviewer was unmistakably intelligent. Interview topics were completely free-flowing - one interview was mostly a debate on the Civil War :-) Interviewing styles were markedly different, but each interviewer knew exactly what they were looking for and most were able to get the information they wanted by making you talk about what you've done in the past, rather than just ask academic questions.
Technical questions were easy, but this was for a position in Ops, so clearly not as technical as engineering interviews. Jargon in resume was deeply challenged by some interviewers. Everyone was very respectful, friendly, open, and most importantly, seemed interested in what I had to say (some were open to broad discussions, others wanted more concise answers).
Only suggestion to candidates would be, shed all facades and appearances and go as yourself. I had so much fun that I wanted to interview some more! I can see how some might find the interviews daunting and the interviewers intimidating, but if you're comfortable with who you are, you'll meet some very interesting people who are deeply, deeply passionate and have an integrated outlook toward work, life and fun.
Negatives: They're going through some logistical challenges in the new offices, though hardly anything out of the ordinary. Depending on who you interview with, the recruiting team may find it hard to assimilate feedback in a timely manner. Somewhat cultish adherence to principles/ideology/Zuck - practically each interviewer apologized for sounding like they'd drunk the kool-aid :) They don't yet realize that they're getting too busy for their actions to always match their words. I'm sure so far they've meant everything they said, but as they get bigger and busier, they should be a little cautious about setting expectations, particularly w.r.t time and responsiveness.
Bottom-line: Truly passionate, honest, intelligent, focused workforce, but individual personalities seemed subservient to the spirit of the company. They'll get the cream of the crop, but easy to understand why some exceptionally individualistic people may turn them down without second thought.