I had a Candyshell Grip on my M7 (and have one on my iPad Mini). I currently have a Spigen Slim Armor on my M8. Looking at your pics, the Candyshell Grip looks to be considerably thinner than the Slim Armor. Kind of makes me want one.
I have dropped my M8 with my Slim Armor. More like, threw it at the concrete, actually. I was pulling it from my pocket at the gas pump, bobbled it, and ended up whipping it at the ground in my attempt to save it. The case took some roadrash to the front lip, but I'm happy to say that it totally saved my phone. And the roadrash has actually become less noticeable over time.
I wonder how well the Speck would have done. I don't mean that to be condescending or to hijack your thread; I legitimately am curious.
That brings me to my next question.
Every, and I mean every, regular Candyshell I've owned has ended up doing the "pencil eraser" effect with the rubber. These weren't bootlegs, unless Speck themselves were selling bootlegs. My two Grip cases haven't seemed to have done this. Can you tell if yours is or is not doing this? The quick way to tell is to rub your finger along the lip. If it rubs off or even feels like a typical pencil eraser, it's gonna rub off.
HTC One M8 Gunmetal
AT&T, Sunshine S-Off, ARHD 8.1, ElementX .19, undervolted, TWRP 2.7.1, h/k audio
Other devices: iPad Mini 16gb, black, iOS 7.0.6 jailbroken | iPad, 16gb, iOS 5.0.3 jailbroken | Apple TV 2 | HTC Liberty, CM10
iPhone 5S (x3), jailbroken | HTC One M7 Silver, S-Off, ARHD | iPhone 4S, jailbroken | iPhone 4, jailbroken | iPhone 3G, jailbroken