I have a PWTS and Clubsports, the ABS rumble works on every driving game on Xbox 360, PC and PS3 that I have played.
I have ABS set to 85% on the wheel, so when I press the brake 85%, the pedal and the wheel vibrate.
It is independent of the game, it is a wheel setting.
If I power up the wheel on its own, with no console or PC on, if I push the brake, I still get the rumble on the brake pedal and the wheel.
When playing Forza, I also get a rumble on the wheel from engine revs, I don't know if this is a PWTS thing or no.
But I would say that the extra $50 for the clubsports is a small price to pay.
I think that braking is where you can make up most of your time, with the CSP rumble, you get a warning before you lockup.
I adjust the potentiometer depending on what I am driving (race car or street) I agree that you get used to how much pressure to apply, but the rumble feature is like having an assist on.
On an ISR review, they said that having the CSPs was almost like cheating.
My personal opinion is BUY THE CLUBSPORTS.