I interviewed with Apple last year, and I wasn't asked to sign an NDA. That said, I didn't actually see anything that would have required one. I didn't apply to Apple - they found me. A year later, I'm still not sure how that happened, since I don't know anyone there. It could have been through a public talk about user experience that I gave (the position was for UX director of the Apple web site), it might have been…
My experiences were similar. I had several interviews with Apple: 1) Several phone interviews for an internship. They don't do fly outs for internships, if I remember correctly. I never finished this process because I took another position before the interviews were complete. 2) Phone interviews and fly out for a position about 1 year ago. The team had good things to say about me, but it wasn't a good fit for either…
I was asked about some problem solving I had to do at a previous internship and I talked about how setjmp/longjmp saved my skin once. The interviewer seemed more pleased in the fact that I was excited about the solution than the fact that I had one.
Unlike you, I found it refreshing. I got the impression that they cared more about passion than obscure technical answers. In the end, I took another offer instead but it was a difficult decision to make.