I received my D1S today and used it for a hike this evening. First impressions are quite positive: tons of throw, lightweight and compact (but a large head), and the price is certainly right at $40 or less. The ano is very rough compared to the D1 and had rubbed off in a couple of spots. I like the tint of the 4000K emitter, which goes nicely with my Wizard Pro warm for night hikes. Time will tell whether it can convince me to give up the flat regulation and longer battery life of the Manker U21, which is now slated for an emitter swap for sure.
Note: when I received the light, the thermal limit was set to an internal temperature of something like 40°C, which translates to about 30°C at the head. That meant the light throttled down almost immediately on turbo and was at practically moonlight output by 10 minutes trying to maintain such a low temperature. I used the thermal config to set the limit to 71°C (~60°C at the head), which is pretty toasty but largely eliminates throttling. In the winter it will never actually get anywhere near that hot when used outside anyway. Here’s a quick plot of the head temperature at the original setting with a shift back to turbo at 10 minutes.