I beg to differ Tom.
I think you might be getting a bit confused. The idea of ABS is not to provide better braking (a popular misconception which causes many crashes) but just stops the wheels locking and allowing steering in a hard braking scenario. Where ordinerally heavy braking would lock the wheels and cause the car to carry on straight regardless of the steering wheel ABS allows less force to be applied to the pads keeping the wheels turning and letting the steering work.
ABS WILL increase braking performance under racing conditions, in the wet in the dry, everywhere.
The key is braking into a corner. A driver can brake later, so late that he can brake into a corner which even the best sorted non ABS car couldn't do. As a car enters a corner, the inside front tire loses grip due to weight transfer and would normally lock up. Without ABS, a driver couldn't brake that deep without flat spotting a tire. The ABS keeps the tires with the least grip from locking up thereby increasing a drivers brake zone.
A properly sorted ABS system would probably shave a half a second off a non ABS F1 car. That's what I remember from 1993. By properly sorted I mean a system that cycles many times per second, keeping the tire on the threshold of adhesion at all speeds.
It's true however that a road car without ABS could outbrake an ABS system but that is because most cars (especially economy ones) only cycle their pads 4-8 times per second which isn't enough if your wheel is turning 5 or more revolutions per second at speed.
