Their HR/Recruiting was definitely more on-the-ball than most after I had been identified for an interview. The interview itself was two 30-minute one-on-ones with people in a similar position at Amazon. I had been warned that the interviews were tough, but even then they exceeded my expectations. Both interviewers used multiple tiers of drilling questions to see if I really knew the stuff inside and out. There were almost no behavioral questions, and we only cursorily went through my resume. Most questions were hard "what would you do if you were in charge of x?"
One of the interviewers was personable and nice, while the other seemed to have a chip on his/her shoulder. He/she made sure to mention where she had gone to school and how many people she was in charge of.
The kool-aid is definitely strong at Amazon, and they're looking for people who will fit in without too much trouble. At the end of the interview, I knew that I had bombed it, but at the same time, I was decreasingly interested in the job. I think those who would gel with Amazon's culture will do fine, and for the rest of us it will be obvious to both parties that it's not a good fit.