I can't think of much evidence that one-handed usage was tops in Apple's mind.
If it had been, they sure as heck wouldn't have put the <back navigation buttons at the far upper left. Or they could've put a physical back button like every other smartphone design on the planet, since Back is used as much if not more than the Home button is.
Not to mention that it's a multi-touch design, which is hardly one-hand friendly
The primary one-handed capitulation they made was to allow double-tap in addtion to pinch zoom.
Well Steve Jobs and J. Ive thought so when designing the original iphone. If you read Walter issac. book there is a chapter on the I phone. They had different sizes of screen prototypes, same as with the i pad. They picked the 3.5 inch size.
The back button being in the corner is a non issue. You can reach all aspects of the screen with your thumb due to the screen size. Apple is number 1 because they think of every aspect of the machine they build, even the design of the internals design that you cannot even see.
A back button on Ios would be nice. I like that aspect of Android on my one x. But it is needed more on Android in my opinion. Ios could use it but it is a not a deal breaker. The useability in Ios more than make up for it.
Even though the One X has a larger screen, browsing on it is not as smooth iOS. I suspect it is much better on stock ICS than the overlay of sense. As much as i like the larger screen of the One X, i constantly am going to my 4s more and more. iOS is simply, faster, smoother and more user friendly in my opinion. But ICS has closed the gap.
There is something to said for software and hardware integration. The CPU is half as fast but runs smoother, uses less resources.
As good as the One X is. The build quality is still not as good as the iphone. Gaps between the screen and body. Mushy power button, etc.
Screen size isn't the only factor when determining useability. I can still type faster pn my iphone keyboard than the One X despite the screen size. the layout was better thought out way back in 2007 than a phone designed in 2012. That should show you how Apple operates. Its not like they could not have made the screen bigger back in 2007.
I bought the One X due to the retina quality 4.7 display. was sick of the 3.5 display. But i realized that isn't the only aspect that make up a good quality device. Do i want a bigger iphone screen, yes. Who doesnt?