So iOS 7 is pretty nifty, with all its flat UI and graphical trickery. This, however, is probably the niftiest bell and/or whistle I have seen so far: if you set a panorama as your lockscreen photo, the camera tracks your eye and moves the image around where you're looking to add perspective.
Check out this Vine. It shows that when you set a panoramic image on iOS 7 as your lockscreen, you can pan around it just by flicking the phone about. Very nifty.