When I put my F-150 in 4wd low range it automatically shuts off the traction control. It not only saves my rear brakes, but since (in the snow) the Blizzaks have to claw through it to hit the ground it goes up the mountain much better that way.
In the Mustang, I always turn off the traction control as soon as it starts, as it is not really compatible with the SC in either dry or snow. Of course, it is a blessing to know how to drive in the snow! With my 2000 Mustang GT, (which was stock), the traction control literally stopped me when going up a snow-covered hill. I had to turn it off, back down, get a running start and go up with it off. Anyone who does not know how to modulate their right foot and counter steer with rear wheel drive should not be driving in the snow! (Or on dry ground with a high HP car).
I believe the traction control in the F-150 (and the Mustangs) is designed for dry pavement and is not intended for off road or the snow. Other systems may be better, but none will cover every circumstance.