I did a cloth simulation and it worked perfect and fast in H18!
The problem I have these days is adding materials and textures to the cloth after the simulation. I add the materials as normal materials node, but it displays as black textures. I added unpack and normal nodes before the materials node, but still nothing working.
ie. sort out your uv/mat..etc..etc…on the initial static geo BEFORE you fed that into cloth. then use point deform to deform that static geo with the result out of vellum.