I'm going caseless for a while with a skin. I put on a dbrand leather skin, and separately ordered a matt black camera bar cover from them, as the leather looks weird on the camera bar to me. Super happy - great grip on the back. Still not great sides grip, but the 6 is better than the 6+ on that. Only think that worries me is nothing on the screen side - not sure of the solution, but a little leather wrap for the face would be cool, but not sure it would be durable. I don't have a different cameral here for a photo, but will try to remember to add one later.
Edit: Here is my skin after 3 months of use. I really like the grip and the look, but lack of any screen protection is an issue. I have 2 small screen scratches, which I have never gotten with a case. Also, scratched anodizing on the camera bar edge. I have started to use a Pelican case from the $5 AT&T deal when I am doing anything active and going with the skin only when I think the phone will be safe. I like the grip a lot, and almost no additional thickness - a case fits fine over the skin.