How to develop or migrate apps for iPhone 5 screen resolution?

Question

The new iPhone 5 display has a new aspect ratio and a new resolution (640 x 1136 pixels).

What is required to develop new or transition already existing applications

Answer 1

I had added the new default launch image and (in checking out several other SE answers...) made sure my storyboards all auto-sized themselves and subviews but the retina 4 inches still letterboxed.

Then I noticed that my info plist had a line item for "Launch image" set to "Default.png", which I thusly removed and magically letterboxing no longer appeared. Hopefully, that saves someone else the same craziness I endured.