Its pretty much the only way to do it as otherwise the supercharger would become something of a parasite.
Yup. Don't remember the exact figures but at high revs on a Ford GT the supercharger is costing the enging a fair bit of horsepower. 50bhp sticks in my mind for some reason. Could be completely wrong. In motorsport it's a big thing when you have 5bhp over the opposition. So to gain 50bhp (just an example) is pretty darn good.