Don, I'm not one of the princess and the pea type of cyclist, I don't notice a difference in two wheelsets that are as close as 500 grams between my road bikes. I do notice a difference between the touring bike's wheelset and a roadie's wheelset because the touring bike's wheelset is possibly 75% heavier (Quick math and just the touring bike's tires are 75% the weight of the roadie's wheelset.).

Wheels are like flywheels, they store energy. The heavier the flywheel the greater is the energy required to spool up to a certain RPM in a finite amount of time compared to a lighter flywheel yet less energy is required to maintain the target RPM. The heavier flywheel will continue to spin longer than the lighter flywheel when power is removed.

Much ado about nothing for the average recreational cyclist. A & B club riders likely benefit from lighter wheelsets and tourers likely benefit from heavier wheelsets.

Brad