I’ve spent the last hour or so thumbing through the archives at Daring Fireball.
Here’s Gruber from New Year’s Eve 2009, in a posit about the then-unannounced iPad. Regarding The Tablet’s OS, he writes (emphasis mine):
The iPhone OS user interface was not designed in the abstract. It’s entirely about real-world usability, and very much designed specifically around the physical size of the device itself. The size and spacing of tappable targets are designed with the size of human thumb- and fingertips in mind.
In the broader context, these sentiments are spot-on. There is one exception, though:
Notification Center -- specifically, the ‘X’-to-close button.
There are two problems here that run counter to the design principle described above. First, the control itself defies usability insofar that it’s so damn small. I have small hands/fingers, and I can’t tell you how many times I’ve missed trying to clear a notification. Second, that little gray X runs afoul of Apple’s reimagining of a computer’s user interface. That is to say, there should be no reason for that X to exist. Rather, a far better, more elegant solution to deleting notifications would be to swipe right then Delete to confirm, a la the Messages app.
Related to usability, Gruber continues:
More importantly, the whole thing is designed so that it can be used one-handed. Even an adult with relatively small hands can go from one corner to the other with their thumb, holding the iPhone in one hand.
The potential handicapping of one-handed navigation is the biggest reason I have reservations regarding the oft-rumored iPhone (6). A larger display in and of itself is a good thing, but not if it comes at the expense of the phone becoming bigger. That would make for a substantially worse experience, bigger screen be damned.