Someone had to be the first to make the two meet.
I really like how this works in an OS X setting. It's gorgeous and incredibly clear. It seems fashionable at the moment to describe this as 'flat', but it doesn't seem to take it too far. It still provides a good sense of hierarchy and separation.
I'm interested to see if other designers take this route and which direction Apple will move in for the official design language of OS X (or OS 11?).