You can't find a perfect OS. Like swiping to delete in mail...you kinda learn the OS as you use it, and thats with almost every operating system. It doesn't always have to be flat out obvious.
Agree with this, and I can understand that it's not always possible to find a perfect initerface solution for a new problem at first attempt. But iOS 7 is the case when they actually SOLVED the design problem and made it (for example lock screen) flat obvious in iOS since the very first version, but then broke it and made it confusing in iOS 7.