In iOS 7.1, Apple changed the design of the shift key. This was the worst thing to happen in the history of software.
When the shift key is on, it blends in with the letter keys. When it’s off, it blends in with the function keys. Neither state sticks out enough to read as active, especially in a split second.
There is a simpler solution to the problem, which is what they did for iOS’ dark style keyboard: make the shift key’s active state different than any other key on the keyboard. It doesn’t matter how it’s different – as long as the active state is unique, it will be readable.
I particularly like his last proposal for a redesigned shift key.