I bought some of those 1.6V Power Genix batteries just to see how they would work compared to the Rayovac 4.0 LSD batteries I have. This is far from a scientific test but gives one a rough idea how these batteries compare.
The Power Genix batteries come off the charger right around 1.87 volts and the Rayovacs are around 1.45 volts as read on my trusty Fluke multimeter. I used batteries that had been charged about 10 days ago but they were both charged on the same day. The Rayovac I used measured 1.36 volts and the Power Genix measured 1.82 volts.
The flashlight used was a Quark AA Tatical R2 set to the high mode which is suppose to give 90 lumens out the front with a single AA battery. I'm impressed with the little light as it easily matches my Surefire 6P LED in output and has a warmer beam.
If you are wondering if the light is brighter with the Power Genix battery it is but not by much.
I started with the Power Genix battery and turned the Quark on at it's Max setting and let it set on the end table while watching Football this past Sunday. According to the literature with the light it should last 1.2 hours or 72 minutes but it doesn't say with what type of battery. The light started to fade at 97 minutes and was fading fairly fast. The battery measured 1.45 volts when I removed it.
I let the light cool down for 30 minutes, it only got mildly warm to begin with. It was cool to the touch when I started with the Rayovac. The Rayovac started to dim at the 87 minute mark and was fading fast.
Fairly impressed with both batteries. When starting I thought if they reached an hour I would be doing good. The Rayovac seemed to be fading faster when it started but neither battery was going to last long on Max. I didn't want to run them on a lower setting until they died completely as I understand that can shorten the battery life drastically.
So are the Power Genix batteries worth the expense of an extra charger and the hassle of tracking a different set/type of batteries. Probably not for flashlight use but they do seem to work as advertised and if you have something that needs the extra voltage they may be the ticket. Just be careful because as I stated earlier they come out of the charger at 1.87 volts or there about and that is higher than the Energizer Lithiums.