When I had a Magnic light rear, I had people in cars and trucks stop me to ask what kind of light it was that was so bright. This was in daytime. The funny thing is that I can't vouch for it myself because I never actually saw it in action, it was always behind me. And then I lost it before I had a chance to ask someone to swap bikes so I could see. (By the same token, I've never actually seen my B&M front light either coming at me, although I can see the impact.) It was a cool light, with no visible source of power.

I have another one coming, if they ever start shipping the Kickstarter batch. This one is supposed to be a tad brighter, and with a flash mode and standlight.