"But if you want to have enough light to get off a mountain in the dark... they you don't want to worry about weight so much as having lots of lumens and a battery pack that will last."
That is the big plus for these fancy multi-intensity headlamps. When you are just using it around camp, you don't need much intensity, so you leave it on the lowest setting and it gets days of battery life. Then for the night trail, you have the medium setting. For a special situation or emergency, you have the brightest intensity, but it gives only a few hours of life on one battery. So, whatever you need to use this for, it will do it.
In August a bunch of us did a Trans-Sierra dayhike at Piute Pass. We started hiking in the early morning darkness, hiked all day, and then finished late that night in darkness. The Zebralight did fine, although I held it low in my hand to get a better light angle on the trail.
As was pointed out, the intensity regulation is very good. On an ordinary non-regulated headlamp, the light intensity correlates to the battery voltage, which begins to decay immediately. With a well-regulated headlamp, the regulator "chops" the battery voltage in a pulse width modulator, and that holds the effective light intensity very constant until the battery is getting fairly dead. This is more important when you are using the higher intensities, since they use more current than the lowest.
Two years ago I got a good night photo of an Idaho wolverine using just my Zebralight for illumination.