Even though Gorilla Glass should hold up to everyday, keys-in-pocket situations, screen protectors do provide a little more piece of mind. And when they get dinged up, you can just get a new one. But the main issue I put one on is that I've found on previous phones that, over time, it seems that oils from your skin and salt from your sweat will mar the screen. I don't know if they become impregnated in the glass or remove one of the coating layers, but when the screen is off, you'll notice dark areas that don't wipe off.