This.My friend dropped hers, the screen still worked so she kept using it, but over time the crack spread and she got annoyed with it, so she took it to the apple store. It was out of warranty, but they replaced the screen for her for free anyway. That doesn't mean that they will definitely do it for you, but it certainly can't hurt to ask.
My phone was just 2 weeks out of warranty and the Apple Store would do nothing for me, except sell me another one for $499
