How nice would high octane gas be?

Those racers would surely have to use appropriate parts..they are not 10% ethanol / 90 % gas.
Don't get me wrong...I have not used it, but i don't know anybody that has problems who use it regularly.I do know enough not to trust the internet or guys that repeat what they read or heard.Common sense goes a long way here.
the best info will come from guys that use it