been using it for in excess of 12 years now and its great. Soft enough that you feel it ever so slighty spongie (sp?) when you walk on it so the horse must feel that too. Its a little pricey but IMO well worth its money
I have some mats that are endorsed by Mary King ( although I had mine first!!!) They are Stable Comfort, basically instead of the patchmats, the ones I have are like matresses filled with chopped rubber bits, you fit these to the full stable and then fit the solid wetproof sheet over the top, it is fixed in place with plastic strips drilled into the stable wall. They are permanent and allegedly the most natural feeling surface for a horse to stand or lie on (it mimics pasture) and some research supports evidence of reducing recovery times for concussion injury. But they are not cheap!