"everything was looked at, everything thought about"

When I went to WWDC this year, the lead UX guy from Apple said that one of their major design considerations is how to make the interface seem like a real thing with which you're interacting directly (known as a NUI in some circles).

If you keep this mind it explains a lot of their UI decisions... For example, the letter headers pushing each other out of the way as if they could not occupy the same space at the same time.