Being afflicted with GAS, (Gear Acquisition Syndrome, as my friend Mike diagnosed a few years back) I bought a set of these lights.  I have yet to test them on a night dive, but have used them at the Blue Hole in Belize.  They seemed to work pretty well for up close wall observations (5-10'), but with the ambient light, it was really hard to tell how well they worked at a distance. 

They are very durable, and quite comfortable, fit like a glove, so to speak.

I have some carpal tunnel issues, so holding a light for a 45 minute dive gets to be cumbersome. 

They will be thoroughly tested by me in the next week or two. 

The light is not directional, so it is not good to spot out things when there is ample ambient light available.  I actually found it quite nice on night dives, because it lit up a wide area and for me seemed bright enough.  Certainlly not as good as my friends big canister lights, but also MUCH less expensive!  I'll probably buy a second light and wear it on my other hand to see how that works

It is very convient having it on your hand.  I wear it and keep it on in low viz conditions so I am more visible to people I'm diving with. 

It is a good back up light, and works as a primary in certain conditions.  You will certainly want to carry around a more directional light for other conditions.

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