Finally, iOS 7 is public last month. The new interfaces are quite different with previous versions. As a developer, there are so many changes, it is difficult to lose ourself. But there 3 themes:
1. Deference. The app should defer to content. It can take advantage of the whole screen. Focus on the content and let the UI play a supporting role. Let translucent UI element hint at the content behind them.
2. Clarity. Providing clarity can ensure the content is paramount in the app. Use plenty of negative space; Let color simplify the UI; Use the system fonts; And use borderless buttons.
3. Depth. In iOS 7, there are a lot of build-in app displays content in distinct layers that convey hierarchy and position to help users understand the relationships among onscreen objects.

Remember these 3 themes can help developer to convert current iOS 6 app to iOS 7 or firstly create app for iOS 7.

For detail, please check the Mobile Human Interface Guidline