Only a week in, but I am using this case. It is pretty minimal but feels nice and does not add much bulk. The phone is slippery and this case solves that.

https://www.amazon.com/gp/aw/d/B01GY95E06/ref=psdcmw_3081461011_t2_B01GDEWS9M

Sorry for the ugly link I'm on mobile. I have this case and it's great. AMA

https://www.amazon.com/gp/aw/d/B01GY95E06?vs=1#immersive-view_1471549018016 I'm getting this case. It's thin and won't offer much drop protection, but if you are just looking to get a grippier back then it looks promising.

I have the Spigen and it's great, just the right thickness for me, not too thick that it makes the phone too bulky, and the buttons are really nice. There is also this one if you want something thinner: https://www.amazon.com/gp/product/B01GY95E06/