It’s amusing how quickly a technological behaviour can be learned and taken for granted.
I upgraded to an iPhone 5S when they came out (from a three year old iPhone 4). In case you don’t know, one of its key selling features is Touch ID. This is a fingerprint sensor built in to the home button, i.e. That solitary button that sits under the screen on every iPhone.
I have been an iPhone user since the start. Building Touch ID into the home button means that the button itself has changed for the first time since the original iPhone in 2007. It is now flat, instead of mildly concave; it doesn’t have a small rounded square printed on it; there’s now an imperceptible extra ring around the button; and it feels nicer.
But most importantly it is useful.