Frasier Spiers looks at the history of iOS:
“Three times in my career, Apple has shipped software that conventional wisdom said basically couldn't be done. The first was the Carbon layer of Mac OS X: most of the Mac toolbox running on a preemptively multitasking, protected memory Unix kernel. The second was Rosetta: PowerPC apps running unmodified and, for the most part, perfectly well on Intel processors.
iOS was the third. Conventional wisdom said that you couldn't possibly get a desktop OS running on a phone. Conventional wisdom said that you couldn't get rid of a user-visible filesystem. Conventional wisdom said you couldn't require all software on the platform to come through a first-party app store.
Right now, just before WWDC 2013, I think it's important to take time to appreciate exactly what iOS has achieved.”
He presents some fantastic data points, then delves into items he believes iOS should improve on for power users. Highly recommended reading, so grab a cup of coffee and go check it out.