Used it a few times now. Decent stuff, I was told the only difference between this and keraquick is that it's not suitable for UFH and it can't be mixed with Latex Plus.
Used the proquick recently, very good price but was not impressed at all with it compaired to the old stuff (kerraquick) i think! It was harder to achieve a good bond with the tile imo, seemed to have a sandyer feel to it and less tacky! Only use it now to flatten out dodgy walls!