I see nothing wrong with only showing uppercase letters on the keyboard as they seem easier to read.

The major flailing is the shift key. Right now it's white with a black arrow. That means the sentence started with an initial cap. At any other theme, say mid sentence, it's different again. Mid sentence it's a white arrow on darker gray.

So, in short: about to type cap? Black on White. Mid sentence? white on dark grey. Want to do all caps? Double tap it and get a new version.

I'm not sure how these semantics are different enough from iOS 6 to cause confusion but it does ALL THE TIME.