I don't like lightened flywheels makes the car rev quick but the downside is less torque and possible rough idle. for a road car i would'nt bother dont forget if you do lighten your fly the make sure its all balanced

Taken from another forum:

The one negative of a lighter flywheel is that it makes taking off from a stop more difficult as there's less inertia. Otherwise, nothing but benefits as it 'frees' up power by reducing inertia and weight, makes rev-matching/downshifting easier as the engine revs more freely, and I'd guess that it lessens the wear on the clutch and tranny on shifts due to less inertia. BUT, it probably increases clutch wear a bit when starting from a stop as you'll need to slip the clutch a bit more.