I prefer this over fumbling around trying to push the "Decline" or "Answer" button. In fact, I would argue that Apple has a better design. Here's why:

If your phone starts ringing in, say a classroom, and its stuck deep in your bag annoying everybody; you don't have to pull it, look at the screen, and annoy everybody even more. Instead you can reach in your bag, find the power button, push it, and be done with it.