No,no,i didn't suddenly gone cuckoo and speak in Shakesperian-language. I just want to underscore as usually pro's and con's of the ABS (anti-lock braking system) in modern cars.
As you you probably know,there are almost no modern cars that come out of production without it. First,the acronyms come from German, Antiblockiersystem and as strange as it might seem,it was first invented by a French dude,for use in the airplane brake system. It is,largely,a security system that prevents wheels lock during hard braking,so the driver can steel steer the car around obstacles.
As you might know,when a car breaks hard,the weight transfers to the fron,due to inertia,so it is possible that front wheels get too much friction and loose traction, while the back wheels get little weight,due to the same inertia. This problem is solved by a new addition,called EBD (electronic Brake distribution) wich tends to distribute the brake force more to the back wheels,so the aforementioned problem is solved.
In theory, ABS is a controller that activates the callipers on each wheel tens of times a second,so the wheels don't lock. Note that tires still screech,so hearing that awful sound doesn't mean the ABS is not working or present.
The controller ,coupled with sensors attached on each wheel,continually monitor the speed of each wheel is rotating with. When a wheel begins to turn slower then the others,it will release the brake for that wheel,so it will pick up speed again,and not lock down. At the same time,if a wheel starts spin too fast,comparing to the others,it will brake down,and thus reduce the speed of the car.
There is no doubt that this system saved many lives,or avoid property damage,by letting drivers steer around obstacles. But sometimes,even the best intentions get critics... So,here i will list,as before,advantages and disadvantages of the system:
What's great:

• Instead of breaking hard,and not being able to steer the car,with the ABS you can securely turn your car.
• On concrete,or normal bitum surfaces,braking is actually improved,and so shorter distances are required to put the car to a halt.
• When used in connection with the ESP (Electronic Stability Program) it greatly deacreases car and driver risk of accidents.

What's not so great:

• Higher cost of manufacturing,and maintainance. This is now pretty much not a problem,as ABS comes standard in the vast majority of new cars.
• In snow,mud,or sand-covered surfaces,actual braking distance is increased,even more than 20% plus !! Normaly,a locked-wheel car would simply sink in,and increase braking,but with ABS is not actually the best choice. This "problem" is solved by adding the ability to disable ABS on demand. Also,newer ABS generation systems are better at dealing with this
• Sometimes,drivers not used with the ABS will brake hard,and when feel the pulsating of the brake pedal,actually remove the foot from the pedal,wich considerably increases the risk of accident. This is due to unfamiliarization with the technology,and not readin the owner's manual. So,this is not a problem.
• Cheaper,smaller cars with smaller tires,tend to engage ABS earlier,especially in sand,snow or mud conditions. This is a problem with older versions of the controller unit. As a solution,it is recommended to purchase and equip the car with better tires,or/and reduce speed on these surfaces.

If you would like,also check this great wikipedia link here http://wiki.answers.com/Q/What_are_ABS_EBD_EPS_in_a_car