well, i double clutch all the time. i just think its fun, but i also want to work on my pedal work, so thats why i do it. i've gotten pretty good at braking and double clutching at the same time its not only a truck thing, in my opinion. if you're racing (not drag racing) its a good thing to know how to do. you know that jolt you feel if you just downshift and let off the clutch real fast? with double clutching you don't get that at all.. if you're going really fast in a race, that jolt probably will be worse. any forces that act in a way other than towards helping you go forward (when you want to go forward) can only hurt.. double clutching gives you a smooth, fast, seemless downshift

but ey, maybe i'm wrong! i don't know everything..