These are the outer layer of my cold weather paddling footwear. I wear wool socks underneath my drysuit socks, and then slip these over the top. I've tried quite a few different combinations of neoprene socks, booties, and socks for cold weather paddling; the aforementioned is by far the warmest and keeps the foot-bulk low enough that I'm still comfy in my play boat.
I'm not sure how tough the kevlar part is, but I think that these will last long than regular neoprene booties. They also seem to have better traction. You'll need tough feet to walk in these on there own, but throw a pair of wool or neoprene socks underneath and they seem to be pretty protective. In any case, I think these have a place in the wardrobe of any regular whitewater paddler.