This morning’s Observer column.

Tuesday would be – so the hype machine assured us – iPhone 5 day. But Tuesday came and went and it turned out to be only iPhone 4S day, and the assembled chorus drawn from the Apple-obsessed region of the blogosphere and the “analysts” of Wall Street howled their frustration. Which made one wonder what these people expected – an iPhone 5 that did teleportation? It also made one wonder if anyone on Wall Street has ever heard of the sigmoid function, the universal s-shaped learning curve that shows a progression from small beginnings and accelerates rapidly before creeping slowly towards its maximum point.

The point is that the iPhone has been through the acceleration phase and is now at the point where it can only get incrementally better. What CEO Tim Cook and his colleagues announced on Tuesday represented an implicit acknowledgment of that reality: they announced an incrementally improved product…