I would definitely agree with Acurasquirrel regarding ABS - in winter. If you have any type of sporty car, chances are it has fat tyres. In winter ABS will make you slide and slide and slide....Saw a very amusing crash once - at all of 5 mph, sliding about 15 feet into a truck. Looked like a safe distance, but the ABS just kept the brakes off.

Without ABS, you can lock which helps braking in ice and snow.

Even in the summer, heavy braking while going over ruts can trigger the ABS which can seriously stuff your stopping distance, which can be very scary if you are trying high-g manoevres, so my advice would be if you are very confident with your car's handling, and drive pretty hard, kill the ABS - the ride will be much more predictable, and safer.