My experience with my 87 BMW (I'm allowed to use ABS in BMW Club Racing) has been that if ABS actuates my stopping distances are increased and understeering off the end of the straight is a good possibility. The only difference I've noticed between using it and not is that if I make a mistake when I have ABS enabled is I don't get a flat spot. Given my experience I'd say its primary benefit is that it is a money saver. Since budget is my #1 priority I'd like to be able to use it all the time.

I also instruct at a lot of BMW Club Drivers Ed events and I can say that every generation of BMW ABS has been better than the one before. The ABS in the current generation BMWs (E46) is very, very good. Even so, given the choice, all the WC BMW teams still chose to go with a 'real' race brake setup.