Has anyone tried a "leather" turntable mat?

No, but interesting and different. I have tried many things both purchased and home-made in an effort to better the sound of my TT of which I already feel is wonderful. I have finally realized that the solution, for me, is not to change the sound of my TT, but to free its sound (IMO). Remove any additves, and stop the normal vibrations and noise that muddies the sound. Once you get rid of the grunge, the TT can now speak for itself. If you don't like what it's saying after that, maybe you need a different TT.

Finally, I found what I was looking for with an SRA Base. This tweak was big for my TT, and when I add a mat now, I hear an additional color that I don't care for.

I heard, those made from Canadian Caribou have the best sound. But it is important that they died happy. Killed from a truck will support distortions ...

I have been using a Victor pigskin mat designed for use on their Laboratory Series DD turntables like the TT-101.
One side is suede whilst the other is tanned leather......very much like the 'Hide in the Sound' mats.
I would avoid the cork laminated leather mats like those from MooMats.
The Victor pigskin mat is 1mm-1.5mm just like the 'Hide in the Sound' ones and produces the best sound from the cast Aluminium platter of the TT-101.......equal to that of the the heavy Micro Seiki Cu-180 copper mat.
I find it best with the suede side up.
The pigskin mat does not sound better on my Raven AC platter. The bare copper top without any mat sounds best in my system......so I guess it is all dependent on the make-up of your platter?
But at the cheap price of $33 for the 'Hide in the Sound' mats....I don't see how you could go wrong trying it out? :-)
If you do......please let us know?

I have a thin Hide in the Sound leather mat on Yamaha yp-82 table. I wanted to drop the VTA and was not in fear of the resonance of the aluminium platter. I am using a Denon mono cart. No negatives. Not muddy nor extra detailed, etc. Looks nice.

I got one of these on my RP6:

leather mat

I think it sounds and looks great. My local Rega dealer said I should put it side-by-side to a $65 Herbie Mat . I've used Herbie Mats on other tables and they were good, but I like the fact that the leather mat is all natural and soft on both sides for the vinyl and the glass platter of the RP6. Maybe if I upgrade my subplatter to a GT and I can use my Cleaver Clamp again, I will try a Herbie Mat after putting in a good amount of listening on just the subplatter upgrade.

Have people done side-by-side comparisons with leather like mine and the Herbie Mat on the newest RP3 / RP6 models?