I'm loving the light. Even in bright light, with it cranked way up it makes the screen look white. Which I love as I never cared for the drab, gray look of e-ink--just tolerated it as it was so much easier on the eyes than a back lit screen.
I find I read in bed (dim room) with the light around 15-16, bright room I'll crank it up to 20-22. Dark room probably around 10, but haven't read long enough in the dark to see if that gets too bright as eyes adjust to dark.