I agree that reducing the unsprung weight on (example) the rear axle will make the car launch better.
Of course, this will only really help cars that have problems now (enough power, but bad chassis reaction), and the problems are small enough that reducing only the wheel weight will give a better result (the axle alone is over 100 lbs., add the springs, shocks, drums, blah and taking 5 lbs. off each rim doesn't do that much).
It will also make controlling the front wheels more predictable - the spring rate can be selected for best weight transfer, rather than how much is needed to control the wheel bounce.
