I've got one, not tried it on the noggin yet. But it is lighter than the older single LED "magicshine" style lights (P7, T6, U2 etc), so would work well for a headlight.
If you want something lighter, then maybe this would do the job (looks 100g lighter according to the shipping weight....)
http://www.lightmalls.com/mini-1-cree-x ... p-cap-onlyT6 LEDs are plenty bright enough for a decent night ride at pace.
It does not however come with a battery, so you would need one of them too!
I don't have the second light, so can't say if it is actually any lighter, but it would appear to be on the face of it. It is the same price as the one VW has suggested though...
If I remember, I'll weigh the unit this evening.
G