I have one and while I now use it mostly for the dusk feature since I don't have to get up I used it for dawn when I was working. I've had one (several different ones as they tend to break) for probably almost 10 years now and they really, really help me. The dusk feature has always been more helpful to me but that's just b/c falling asleep is so hard for me.

I would recommend reading reviews and getting one that holds up well. It's worth the extra money. I had one for many years that died last summer and I went through 3 cheaper ones before giving up and getting the more expensive one that I had before (which wasn't expensive when I got it). This is what I have:

http://www.amazon.com/BioBrite-Pearl...dawn+simulator

Anyway, I really do love the thing. It's probably one of my favorite things I have for bipolar. I just hope this one doesn't break for a long, long time (I did break the glass dome one day but that was a freak accident; it never happened with the first one and it's easily replaced, just annoying if it happens which is probably only rarely does given what it took for me to break it).