The Diablo is a fantastic light. A bit heavier than their other options they show for head mounting.
Learn to switch the program modes. I think I have mine on 3, gives me a long long time on low (perfect for a camp light...).
I use it often on the bars with the bar mount when I'm not on the dyno equipped bike. Plenty of burn time for my local loop riding on medium, and I can switch to high as needed.
Also, this thing is silly looking as hell:
Improvised by
Mike, on Flickr
I don't run it when I wear the light on my head, but I had to emergency zip tie that light on for that trip, so my camp light stayed on the helmet.
Really diffuses the light. Pick one up if you camp. Hung from the tent, bars, tree branch, etc. it really lights up camp. Here I'm making use of it to finish cleaning up the yard:
Because dark and work needs doing... by
Mike, on Flickr