I have one, and I can't tell if the car revs up faster, as it should with the less rotational mass the alum d/s provides, but I can tell you that there are less vibrations when the car is rolling. For that alone, it was worth it.
Definately worth it in my opinion. A great thing to do if you put gears in only because the stock POS vibrates like crap at high speeds, or if you drag race often or auto-cross. Less rotational mass makes it so much easier for our little 281's to rev.