iOS has barely changed in UI since it's inception. That's not a good thing. No one designs the perfect design the fist time, nor the 100th time, nor ever. The goals and targets change and the design evolves. There has been no evolvement.

Sure, there's more precise releases than it's competitors, but that doesn't negate the fact that Windows has a more functional-looking (whether or not it is, is an entirely different matter) phone.

The Notification centre was a step in the right direction, but people are wanting data quicker more and more, and the notificiations aren't great for every app. After all, a big reason people cite for going for Android is customisation.

When the iPhone was released it was the absolute leader in mobile iOS among other things. Now it's a solid competer but it lacks the originality it once had.