I have not had any issues at high speed stopping with these brakes. I've got on them at speeds around 130mph and no vibration, shimmy, ect with good rotors/pads.
Side note: I have EBC rotors and pads, they are not cross drilled, just slotted and dimpled. My buddy has the same on an '02 WS6 and has got on the brakes at 160 mph with no problems as well.
HTH