Dropped my GS4 once from about waist high as I was pulling it out of my back pocket. The end of the case snagged my pocket and pulled it out of my hand just as it cleared the pocket. It tumbled to a tile floor. No damage to either the phone or the Speck case.
I dropped it again about a week ago when I stopped the car and forgot it was in my lap. It tumbled to the concrete. No damage to the phone or the Speck case.
I believe in the value of a quality case.