Marco Arment published a post on his blog which I completely agree with:

If you want to enter a category that’s crowded on iOS 6, and you’re one of the few that exclusively targets iOS 7, your app can look better, work better, and be faster and cheaper to develop than most competing apps.

As iOS developer, I got really excited by this year’s WWDC: an ecosystem that feels new and mature at the same time and a tons of new API to learn and play with.

If you’re developing an iOS app, please make sure to use some of them if you’re hoping to be noticed by Apple.

These are my favorites:

• UIKIt Dynamics
• UIViewController and UICollectionViewLayout transitions
• Background fetches
• Push updates

I think I’m going to dive into UIKit Dynamics and new view controllers and collection views transitions as I think this year the challenge will be about thoughtful animations.
After that, I’ll probably check whether they really fixed iCloud and Core Data.