[fohlin]

I have used that exact Wake-Up light model for about a year. It has had a marginal effect, in that I wake "naturally" (before the sound alarm goes off) about 1 night in 20. As a simple source of bright light, it performs as you would expect -- with the extra benefit that my tired morning self does not have to bother with turning it on.

I would rank its usefulness above 0, but below a consistent bed time, and so far, below vitamin D (3250 IU in the morning).