You usually will see up to 30% increase on the wacky juice, but like Fred said, it attracts water ( it actually pulls water out of the air ), and uses a shitload more fuel...
You have to deliver it faster, which means a much larger carb, larger jet, etc, fuel line, etc, and you have to watch out, because it eats up rubber like mad. You'll need to replace all the rubber gaskets with some made for alchohol use, which isn't cheap.
Not worth it... unless your doing it for $hits and giggles.