My dad taught me about the heel-toe. I had never heard of it. It is actually quite useful. I don't race by any means but when your driving a manual and you want to have fun with it, its fun
He had a Suzuki Sidekick, it was such a fun little car. I learned how to drive in it.
ALSO: I'm not sure if this is 100% true or not but I'm assuming if your going to do any sort of street racing and your car starts to roll forwards or backwards, using the heel/toe will enable to keep your car 100% still as well as rev the engine up. on the drop you just have to be sure to move your feet quick.
My 2 cents