Yes mate, occasionally in the past, but mainly used them this year over instead of acrylic, alot of people shy away from them as they are hard to put right if they are installed wrong, but the trick is to just do it right... lol. wait untill the surface is completely dry, they must be rolled on so that you 'flood' the joints and the sealer penetrates deep into the sand and when they are set they are absolubtely ROCK HARD mate, you could pressure wash the area with an industrial power washer (around 200bar/15lpm) the year after and the sand will satay put, inlike acrylic which would wash out, therefor saving the customer money as you dont have to resand and the wont be as much mess, pricing a clean the same as you would flagstones really
Acrylics are designed to bond the jointing sand and seal, polyurethanes are designed to PERMANANTLY bond the sand.