I now have!
Happened to me last night. L&M ARC's will cut to half power at 60 seconds to go. 1:11 (I wasn't on a fully battery) in to my ride last night, I'm going along at pretty good pace through the TNT trail (about where the southern most T-N-T is on the map) on my way out to the car and boom - my light dims. I was only about 15 minutes away from the car via the trail, and thankfully the moon was shinning 'cause I didn't have any backup light. It's amazing how much of an effect clouds have on moon light. It was starting to get partly cloudy toward the end of the ride, so I got to see the full effect of it. If you're out there over the next few days and see some footprints that look like Sidi's with toe spikes, that's me! :)
I'll be headed to the store real soon to by an LED headlamp :) Any suggestions?