May be the second time I've found a genuinely insightful piece by Gruber. Skeuomorphic design was a nod to my non-computer using father in the 90s. It no more represents useful metaphors for interfaces than steam engines represent a good way to build cars. iOS is stagnant, reviews of recent Apple designed skeuo-heavy apps bemone the lack of functionality -- while noting what must be hundreds of hours of graphics work…
"iOS is stagnant" iOS only seems stagnant because they don't have to trumpet every year about how they've finally gotten rid of ui lag or completely overhauled the system appearance. These are points in it's favor to most people.
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.