[iainmerrick]

This is still a lot more work than it ought to be on iOS. It's possible to write screen-size-agnostic code, but the tools push you towards individually customizing everything for each of the current screen sizes.

For example, in Interface Builder there's a toolbar with buttons to switch between different screen sizes. But it would be a lot easier if they just made the UI freely resizable (in Interface Builder, not necessarily on the device).