In iOS 7, interface deference is a big thing: Just getting out of the way to enable you to get things done with a minimum of muss and fuss. That concept is employed readily across the board in iOS 8 and Yosemite, where the emphasis is on letting users work as seamlessly and easily as possible without getting in their way.
To me this is the most exciting thing about WWDC 2014 announcements. Being able to work in the same way regardless of the device I happen to be with in that moment.