Well, you'll get 3 hours of light higher than 70 lumens(80 on a new set, then slowly lowers to near 70 after 3 hours) and then it drops off and flattens out into a tail when viewed on a
graph. This is because the LED becomes more efficient as the power being sent to it lessens. Instead of the filament bulbs that die pretty quick, the LED tails out for about 12 hours of total runtime. You can keep the partially depleted batteries and use them for when you don't need tactical level light.(walking to the bathroom in the middle of the night with 80 lumens can make it hard to go back to sleep!)
And yes, rksoon, the G2L is just as waterproof as the regular G2. The only difference between the two is a different emitter. And for some reason unbeknownst to me, Surefire put an aluminum bezel on the G2L. They say in their catalog that it is to dissipate heat better, but the LED puts off zero heat. If you turn on one of the incandescents and keep it near a sensitive body part(fingers, arm, lips, ears, etc..), you can feel the heat coming off of it. The LED has no heat coming off of it. Which is good because extended use in warm temps can shorten the life of the LED. And the incandescent too, for that matter.
Once you have had a real flashlight in your hands, you won't ever go back to the crap ones.
Enjoy that G2L!!