GL4 is the model from Pila that identical to M90. The price of CR123 isn't really bother me too much. As you know, when a light says its runtime will be 60 minutes, it means 30 min real bright and white, then 10 to 12 min dimmer and a bit yellower and then .. etc. I am not too comfortable to trash a set of 123 that only half depleted or to stand 6 series brightness at the size of 9 series light for half of the time.
Having rechargeable, I recharge it at the end of the day regardless 20 min or 40 minutes was used for the day and always have the light in brightest mode the next day;-)
Besides, I like its 9 series beam pattern more than SF's 9 series. I replace the P90 in my C3 with 9v lamp from pila. It's brighter and much whiter than P90 while P90 seems throw further but yellower.
Alan