underdrive pulley

i was looking at getting a zzp underdrive pulley. its just lighter i guess. what would you say is it worth it or not? http://www.zzperformance.com/zzp/products/prod_underdrive_pulley.htm

I have the waterpump underdrive and the alt 5% overdrive.

The main thing about the water pump is that it is so light compared to stock. Dont know if I gained anything from it, but has to help getting rid of that extra rotating mass.