I bought a new Princeton Tec Apex 3 headlamp, their nice waterproof model, and trained with it a bit before heading down to Patagonia. Here is a detailed review of the Apex: http://flashlightreviews.com/reviews/pt_apex.htm. The Apex is great and I thought I had the light issue under control.
While my Apex worked as advertised, for the short 2 hours on "uber high burn" it was not bright enough for our team to make out ridge lines and other helpful features when trekking at night. Don't get me wrong, the Apex is a bright light, but the dense vegetation and deadfall that we battled through made night visibility very tough . . . and it's because of the dense obstacles we found that we really needed as much light as possible! We'd climb and snake our way through 100 meters of downed trees, only to find a 40 meter crevasse plunging away in front of us; in the daylight, we could usually make out the depression ahead of us and work to circumvent the crevasse but at night we stumbled straight into the feature (you see, trekking maps with 1:200,000 and 1:100,000 scale mean you never see features like this crevasse coming). In the daylight, we could at least try to pick the cleared peat bog regions to move through but in the dark it was impossible to identify those areas from any significant distance. Even with our high-end "adventure racing" lights we were slowed to a snails pace at night because all we could do was follow a bearing (like 100 degrees) and confront whatever obstacles lay in our path. Here's one of Sherry's photos showing the typical terrain we plowed through:
We were caught in a trap where it was generally too cold at night to sleep with any comfort, but too dark at night to move with any efficiency. We ended up either not sleeping at all and powering through the darkness, in an effort to make up time on other teams, or just "sleeping" a couple hours at late at night which amounted to laying on the ground and dozing a little until the pre-determined wake up time. Here's a shot of me at one of our "campsites" as the sun was just coming up:

Strangely, I can't wait to race again (and prove I've got a solution to my feet problem!).
Now I will say this for our "no sleep" strategy: we did make up ground on teams. By Saturday (day 5 of the race) we found the Argentine team was several hours behind us and heard rumours that one or maybe two other teams were in the same area as us or just a bit ahead (these are teams that started this monumental trekking leg 12 hours or more ahead of us). I wouldn't call it a brilliant plan, as it was born out of necessity, but it was helping us get to the next CP faster.
I'll explore my sleeping/tenting choices in a different post . . . I want to keep this about lights . . .
I've learned that the winning team from this Patagonia race, an experienced bunch with Eco-challenge and Raid pedigree (with a token American female Ironman -- or is it Ironwoman? -- who had never done an AR in her life!), used a "giant headlamp" to quote the race staff I spoke with. One teammate had something home-grown, but as bright as a car headlight apparently, with an enormous battery pack on his head; the guy in charge of the maps had a smaller light so he could easily read compass and map information; I don't know what the other two teammates used. Apparently, this "giant headlamp" lit up the forest so they could pick more efficient routes through the dense vegetation. This is what we needed! This is what I thought my Apex would do . . . but I learned otherwise!
I think the problem is that when considering headlamps, I went to the usual sources and shopped for a consumer headlamp. An adventure race like this is so far removed from the typical consumer/recreational headlamp experience, that I was doomed to disappointment. I have some HID bike lights that would've been helpful during the trekking leg, but they were stuck with our bikes. In hindsight, I should have brought all my HIDs for the trekking portion of the race! Or, like the winning team did, I should have explored other options for lighting; there are do it yourself guides out there for rolling your own lights and I'm willing to bet if you strap enough batteries to your head you could get a darn bright light!
This is something I can chalk up to our inexperience. I was doing an adventure race, a big one in Patagonia, so I found the best "adventure racing" headlamp out there. What I didn't know is that the Patagonia Expedition Race is a Survival Race and all the usual rules are thrown out the window. Who cares if the light is bulky and ugly, if it can help you discern routes at night through stuff like the following:
. . . it's a good light and I'll be using it instead!