I was a bit surprised to have a non-developer ask me if it’s going to be hard to get my apps to work well on the iPhone 5’s slightly taller screen, and for tech writers to talk about the fear of screen introducing Android-style “fragmentation” issues to iOS because of it. The answer to will this cause problems when developing iPhone apps is no.
iOS developers have all the exact same tools at their disposal for dealing with different screen sizes as Mac developers, and we’ve been dealing with different window sizes forever. In fact, it’s easier, because on the Mac the user can resize the window to pretty much anything they want and on iOS we have a maximum of three sizes we really need to worry about, both of which are easily testable.
A lot of iPhone apps already can deal with at least two sizes (portrait and landscape), and that most apps I use primarily consist of table views (lists) which will stretch automatically. Generally speaking, even badly coded iPhone apps are going to tend to be more flexible vertically since they probably use table views, and the system will handle show extra rows for them.
In all of my apps, the only change I needed to make to support iPhone 5 was to add a new launch image for the taller screen size and submit an update.