I've got one of the H600w II. Uses the 18650 battery. Love it. On the lower powers it is plenty bright, lasts a long time, and doesn't care how cold it is.
I got a single battery recharger that does 18650 lithium, AA NMH as well as AAA. It charges via USB, is ultra small and can be powered by my battery pack in the field.
My only complaint is you have to have the thing on a brighter setting to be able to see while walking through the woods. Of course, that kills the battery.