Not a bad case. Bought it to replace the soft case that comes with the HTC One M8 in Europe. The soft case after about 6 months use had started to warp and break, letting grit in around the back to scratch the aluminium.
Well, this case seems well made. I've previously used an Urban Armour Gear case, which to be fair felt a bit more rubbery and rugged. The SUPCASE seems to feel like a lighter-weight plastic (lightweight = good, but also feels cheap and less durable) than the UAG case.
What this case has over the UAG though, is the front screen protector. It's quite flimsy looking, but at least it offers a little protection. Not sure i'd test it against keys, like I have with ZAGG protectors. Another issue with the protector is that it doesn't "stick" to the phone screen. This was fine at first, but now there's a small portion of the screen that seems to be making contact with the protector. You can't see it when the phone is on, but it's very noticeable when it is off.
Overall, I feel this case will protect my phone for most situations. It's a bargain, but it does feel a little more cheaply constructed than other cases I have used. I also think they may be missing a trick by not offering more colour combinations!