Really.. is it only 500g per hub saving? Your almost better off not eating big-macs for a week and you'll save yourself money and be healthier for it!
I don't think i would bother with such little saving. I know its unsprung etc etc..
Think id only do it if everything else was lightweight like perspex windows, fiberglass boot bonnet, guards & doors etc. and i was itching for an impulse buy.

I conjunction with 2 piece alloy hats might make another small decrease in weight when compared to the same sized integrated cast item.

But they look purdy!
 
Matt