Redstuff are OK but there are better pads. I have been racing on them and they stop the car fine. They don't cope well with heat and when I took the last set off my car they were crumbling but very thin. They don't wear well either. I've had yellow stuff at the front for a whole season of racing and I've gone through two sets of red stuff pads at the back.
They're OK but not special. For serious pads - and seriously expensive - go for Ferodo DS25000 or DS3000.
Charlie