Jordy, I wouldn't build an esky without one. In my opinion, they make the car so much easier to catch with just a quick wrist movement, but if it does go all the way, its also easier to get the steering on the bumps stops with less shuffling of the hands and faster.
Sure, if you can move your arms quick enough, you will be just as good without one, but for the rest of us mortals, I reckon they are great.
Ash