Interesting thread!
I have read with much interest in particular K1.
I run in the dark a lot in this season, and I run a lot in the wood, in this days with snow on the trails too!
I'm testing some headlamps for this use,
PT EOS,
Petzl Myolite 3,
Petzl Tikka Plus (newer, + 80% brighter), and, in this days, latest purchase,
Petzl Tikka XP.
In wood it's important to see little thinks on the trail, example a root, stones under the leafs, and other thinks, this for not stumbling, for this reason a good light quality is useful, more than the powerful.
For me it's important also a beam not too much narrow, for example, if there is a tree down (or a big limb) in the middle of the trail and you are running, is more useful a wide beam rather than a narrow beam, because you see in less time were you pass.
Sometimes I run in large trails, but other times I run in little little trails, or off trail, and these points are much important.
I hope you understand all... with my poor English!!!
PT EOS has the best light quality between my headlamps, the only problem is its narrow beam, but I will change soon stock optic with IMS 17mm reflector.
Petzl Myolite 3, the weight is more high than other my headlamps, but its weight is good for a hybrid headlamps, a benefit is than if you use long beam there is not a little time limit, like, for example, Myo XP (20 seconds), but I prefer lamps more lightweight for running.
For me this lamp is good for hiking.
One note: a strange view effect there is when I switch from led light to halogen light after a long time with led light, this halogen light is much more depth, but is yellow, the first sensation is than it's less bright, however after few seconds my eyes adapts to this light and I see very well.
Petzl Tikka Plus is a good headlamp for running, the quality light is not the best, it's little bluish, but the eyes adapts fast to this light.
This lamp is lightweight, its beam is very wide (I like this feature), if there isn't need of depth view this is a good headlamp for running and it has great autonomy.
Usually I use medium setting, it's enough for most situations, high occasionally, and low when I run on main roads or... on the snow! (for snow refraction)
Petzl Tikka XP, for me this lamp is very adaptable to many situations, I like diffuser use, occasionally boost mode is useful, its light quality is less good than EOS quality light, but it's a good lamp for general purpose!
Its features are like Petzl Myo XP, less powerful, but more lightweight, so don't need top strap like Myo!
Its waterproofing is not like EOS, EOS is very good in this feature, but it is already good!
I'm testing this headlamps, I will write my personal impressions.
Other than these headlamps I have two other, an older Petz Zoom (companion of 1000 adventures! But now it "rests" in my car, for emergency), great lamp but today too heavy and with poor autonomy, and another anonymous led headlamp, low cost, but low quality! (in particular poor light quality).
It has been a mistaken purchase!
Bye
Luigi