It's essential for a perfect carb up pre contest. I start my carb load on the Wed before the show and will continue right up to the show. You need to know how to use it and what effects it has on you. Granted on a proper carb load you're taking in a shit load of carbs. Most people don't realize the amount of carbs necessary to truly supercompensate. That's why most competitors get on stage looking flat, small, and depleted. If you've ever been supercompensated, you'll know what I mean. You feel huge and when you train, your pumps are orgasmic...
So, yes, I use slin precontest for the carb up, and have all my male BB's that I help do the same.