I used this on two shoes:

An old pair of oxfords that are too comfortable to throw away, but got tired of soaked feet everytime it rains or i stepped through any small puddle. They were black matte, applying this gave it a bit of a glossy appearance but not overly. Was just able to tell that they looked a bit different afterwards. I only did one coat with these, wanted to be "gentle". Afterwards they worked surprisingly well! Was able to splash around in some puddles or be out in the rain without getting nearly as wet - obviously some still seeped through probably mainly the tongue area.

An old pair of merrel hiking boots. The material on the outside had torn, and I've already repaired it twice with thick silicone glue to rebond the surfaces. However water still soaked through (these were waterproof previously). I applied two layers of this, with about 6hr inbetween the two, and let dry for two days. Afterwards I could literally stand in 6" of water and my feet not get wet at all. Was definitely surprised on this test, did not expect it to work so well since it had been a couple years since those boots had been that water tight.

I don't know how long this product will last, only time will tell. For now though this product was definitely worth the money - breathing some life and use into some old shoes.