Well these are from Apple Store reviews:
"I have dropped my iPhone a few times on the ground or tile and the iPhone is fine. The case does scratch easily on the back, but hey, its better then the scratches being on the iPhone itself."
"The phone was flung into the air like 3-4 feet high and landed 5 feet away from me after taking like 5 horrible bounces and skidding on rough, rocky pavement. The case stayed intact and took all of the damage (afew big gashes) but the phone was fine and nothing cracked!!"
Main reason I was wondering. I too would have thought this thin faceplate case would be useless...but it seems not. Wouldn't be as good in a drop as the Otterbox would of course, but the reviews seem to indicate it's better than you'd think?