Is not really 100% flat with no drop shadows as everyone says.
Pulling a few images from Apple's public preview site: http://www.apple.com/ios/ios7/features/
The best example is the simple switch. The button part is raised.
Same for the button on a slider control, which is easy to see in this screen.
There are others, type and hold on the onscreen keyboard on an iPhone, the popup letter that shows what you're typing is raised up as well.
Not sure why these particular things use a little shadow and nothing else does...