With the passage to the 4 inches screen size, Apple has insisted that this doesn't change the way people type with their iPhones. However adding a quarter of an inch of screen width wouldn't have changed much to the way people type, especially when a lot of people type with two hands.
On the other hand, adding height to the screen poses a big problem regarding the top buttons and especially the back button in the upper left corner. This button is extremely used and, contrary to typing, most of the time it's used while operating the phone one-handedly. Now that button is really difficult to reach and forces the user to employ an uncomfortable movement of the hand to press it or, more commonly, to use the other hand.
The UI was thought for the previous form factor and iOS hasn't been completely rethought when they made the screen bigger, at least for this problem it's apparent. Even promotional material for the iPhone 5 shows tons of examples where the user's thumb is clearly too small to reach the back button easily.
Apple had to make a bigger screen, now they need to rethink some of the functions of iOS to take advantage of the new size in different ways than those currently implemented. Maybe move the back button to the bottom (that would mean a total revamp of many apps), or give the option to flick back with a gesture for people who want it. There's always the option of a physical button, but everybody knows that's not going to happen. Maybe making the screen larger would have allowed to put a back button at the bottom left corner, without disrupting existing buttons.
That's the problem that's plaguing me. It may seem a minor problem, but that back button is so widely used in iOS, that it's a bit annoying, and the more I think about it, the more it's annoying me.
I added examples for the ad (ok there's an image that's doubled but you get the picture...)
Edited by ClemyNX - 10/16/12 at 7:31am