Looks like this l.e.d. would work great for replacing 100 watt bulbs or 23-26 watt (100 watt equivalent) florescent bulbs. 15 watts is at least a 8 watt savings over the 100 watt equivalent florescent bulb or about a 35% reduction in power consumption (probably less after circuitry losses). If these are cheap enough to use more than one per bulb, we might get closer to 150-200 lumens/watt efficiency for the bulb.
For longevity reasons these would probably be run at no more than 700 mA ( ~8 watts ). That would imply at least 2 in a 100 watt equivalent lamp. At 700 mA, two LEDs of any bin G4 or better ( or G2 if you can reduce the die temperature) would put out enough light to match 100 watts of incandescent.
If you look at the best currently available bin (J2), you can more or less match 100 watts of incandescent (1600 lumens) with any of the following:
1 LED @ 1250 mA - 107 lm/W - 10.2 watts waste heat
2 LEDs @ 550 mA - 126 lm/W - 7.9 watts waste heat
3 LEDs @ 350 mA - 136 lm/W - 7.0 watts waste heat
4 LEDs @ 250 mA - 144 lm/W - 6.3 watts waste heat
5 LEDs @ 190 mA - 153 lm/W - 5.6 watts waste heat
8 LEDs @ 115 mA - 163 lm/W - 5.0 watts waste heat
10 LEDs @ 85 mA - 178 lm/W - 4.2 watts waste heat
Note that I assume Tj of 85° in all cases and use a LER of 330 lm/W to calculate waste heat. Most like Tj would approach room temperature at lower currents, meaning efficiency would approach 200 lm/W. In any case, you're looking at 10 LEDs to reach maximum efficiency. For economic reasons this wouldn't make much sense. 2 to 4 LEDs seems to be a good compromise between cost and efficiency.
I was hoping that I could get an l.e.d. flashlight with a 200+ lumen/watt l.e.d. once they became available. I don't think this l.e.d. will be going into many flashlights anytime soon. I think my best bet is to wait for higher bins of the XM-L2 as they become available.
The voltage on the XM-L2 is also better matched to the typical lithium-ion battery voltage. The MK-R would require a boost driver in most cases, sacrificing efficiency.
With the voltage being near 12 volts, these may also possibly work for car l.e.d. headlight, power failure lights, and low voltage lighting.
These are definitely suited for automotive use. Because the forward voltage is only about 1 volt less than is typical for most automotive electrical systems, you can get away with a super simple linear constant current driver and still have ~90% driver efficiency.