Dr. Drang:
Despite all the talk of flatness—and there’s no question, the icons and certain other parts of the UI are much flatter—this gives iOS 7 as a whole a greater illusion of depth than it ever had before. The shadows and reflections of today pale in comparison. If Apple can enforce, or at least encourage, a consistent use of this new depth, our experience using iOS devices will improve because the software will seem even more physical.
It may seem as if this bucks the current anti-skeuomorphic trend, but it doesn’t. Skeuomorphism is giving an object a non-functional ornamentation that mimics the functional feature of another object. The much-derided green felt of Game Center and the stitching and leather of Calendar are examples because they don’t do anything. Parallax’s illusion of depth, if handled well, will do something: it will organize iOS’s increasing complexity in the mind of the user.
Recommendation: ignore anyone who refers to iOS 7 as simply a “flat” user interface. It is certainly flatter than previous versions, but all of the small details - such as the parallax feature Dr. Drang mentions - give a sense of familiarity, depth, and order.