They won't be using it at all mate. Most racers don't use it when braking hard in a straight line, as literally all of the weight is right at the front of the bike - using the rear just unsettles it. They use it in the wet though, and for certain will use it occasionally going around a corner to tighten their line, or keep the rear from spinning up from under acceleration!
I use mine on my Fazer 6 and did on the 1000, but the Ninja 9 I had before that I didn't bother - apart from low speed manouvering where it was useful it was pretty much redundant, as under hard braking on that with the aftermarket 6 pot Nissin calipers I had the rear was barely ever on the floor!
