Overkill

do you think, i have some DIY lights that kick out 800 lumens. and that is without a helmet light.

Overpriced

It can't be overkill if it keeps you safe or keeps you riding at high speed. There is no such this as Too Much Power

for that price you can get the Hope 4leds that come with a Lithium battery, the ones on that website come with a NiMH battery which is heavier and can suffer from the old memory effect.

Imagine face planting onto the heat fins on the back of that - you would look like you'd gone through a meat slicer!!  *Ouch!*

You'd have to be pretty accurate with your faceplant considering the light unit is only a little bigger than a Quarter (10p aprox)

As for the battery materials they've given a pretty good explanation for it on their site - I certainly don't like the idea of a Li-ion battery popping on me Not that I've ever seen it happen... but if they say it it must be true.