> How is the iOS7 redesign different to that of Android
> and Windows Phone redesigns?
Which specific redesigns are you talking about?
As for iOS 7 redesign, it is interesting, because it goes deep. Apple changes the way it thinks (and iOS devs should think) about the UI and the application contents. Content now receives the most prominent position and UI chrome goes into background. Apple also promotes the "depth" (anyone calling iOS redesign "flat" has no idea that they is talking about and is not worth listening). With the concept of depth interaction and navigation patterns will also change.
Make no mistake, this redesign is not superficial and it will bring a lot of interesting things in the future.