My experience is limited........ but for what it's worth I have/edc a Surefire Aviator A2 and really like it. It does fit your request for a high and low setting but unfortunately uses the CR123A batteries. Mine is the older model with 3x led's in low and those plus 1x halogen bulb in high. The new models specs are:
Max Output 120 .0 lumens
Low Output / Runtime 10 .0 lumens / 15 hours
Tactical Runtime* 2 .0 hours
Length 5 .40 inches
Bezel Diameter 1 .13 inches
Weight w/Batteries 4 .3 ounces
Batteries 2
123A
The low setting is awesome since it doesn't blind you or super-spotlight what you're doing at night. I have G2's mounted on all of my rifles but they sure burn fast (120 lumens for 2 "tactical"? hours). That Lumamax looks like a good buy.
Godspeed