Cygolite Daylightning mode

I don't currently use a front light, just a tail light. As I ride, I see other riders coming toward me and I am amazed at how visible they are at a distance with front lighting. I don't ride at night, but I often go out just before sunrise. Also, I ride on heavily shaded roads with lots of contrast. I want to be seen. So I am considering one of the Cygolite Metro front lights, because I like the idea of its Daylightning mode. Good name! And it seems to have a long runtime, reducing battery recharges.

Any thoughts about Daylightning as a Be Seen light? Also, these lights are available in a few different brightnesses at different prices. The 850 lumen model is $40, and they do downward (and upward) from there. How much brightness is needed for optimum visibility?

Thanks!