One of my favorite features of KitKat is the new Immersive Mode. But... the only apps that actually use it are Play Books and Google Now. (YouTube and other video apps don't count because they've always done full screen without the nav bar).
I find this really disappointing because apps that could really benefit from it don't have it at all. Only 2 apps, seriously? Not even the GALLERY app of all things does Immersive Mode! WTF Google? Add the fact that tablets only get half the KitKat features phones get, and KitKat feels like a huge, over-hyped ripoff.