I've interviewed with Amazon several times in many areas over 6 months. Most were of a casual nature, as my connections came through a mutual friend. I have not had their 5-6 hour round robin interviews. I also interviewed once with a top recruiter at Amazon. I happen to know quite a bit about Amazon, as I have prepared for interviews by meeting people I know that work there and probing for their hot buttons, learning about their culture.
I'd describe their culture as follows: Most important is that they are very customer centric, to the point that they will lose money on transactions before they'd disappoint a customer. Also....driven by metrics, very results-oriented, want people with a bias toward action, want to move fast, want people who will take ownership, people who are comfortable working across departments, want you to be innovative within the Amazon context, which often will manifest itself in streamlining processes. Amazon is very demanding of it's employees and the culture expects 'facts' to support your position, not gut-feel. Writing white papers to support positions are also a part of the culture.
I found Amazon frustrating to work with. Part of the culture is feeling no responsibility to return e-mails or phone calls to candidates. Rather than say they are not interested in you, they prefer to not respond. I'm quite sure they are directed to do so.
I'd note that it's a fairly young culture (20-35),... and I am not.
