[jamn]

Of course the complexity will increase as a function of the number of features.

However, I'd make the following claims:

(1) Some of the functions are simply not that used. You can get by perfectly well without knowing what double and triple clicks on the home button, for example, If you don't know they exist, you will never even notice.

(2) iOS has less features than Android and arguably this makes it somehow less powerful but also less confusing for my mom (e.g. no task manager, no intents).

(3) Switching to a Mac was actually quite challenging coming from PC land ("where's maximize?", "where's a working Alt-Tab?", etc). I'd say the usability still kicks in as far as how easy it is to do your job for most after the learning curve has passed. Your mileage may vary, but I find myself enjoying using my Mac more than I ever did using Windows on my PC for usual tasks, and that's part of what makes it usable for me. I'd expect a similar phenomenon with iOS.