I happened to be interviewing with Google and Yelp at the exact same time, so while I won't directly reference the other two companies this is relevant info for understanding what stood out about the Apple interview process.
First, the hiring manager was surprisingly forthcoming about how the process was moving and how I was doing compared to other candidates. This was incredibly welcoming though it probably had to do with the fact that they were in a rush to hire.
Second, the process was shockingly unorganized. Interview rooms weren't booked, people didn't know when and where they were supposed to be meeting me, other groups kept trying to access the interview rooms and there was no one on-site who was obviously coordinating the process.
Third, Apple wants you to meet with as many people as possible. I met with almost 20 different people during the course of the interview process. You definitely got the vibe that culture fit is highly valued.
Fourth, every single interviewer asked me "Why Apple?" With a 100% ask rate, I am guessing this is the rule.