Just got my hi this morning, charged up the bat and am currently playing with it.
First things first, this is my real first neutral white light and I'm not really liking it. The tint looks way too orange and gives me the impression I've got cardboard walls. My walls were painted some off-gray color so that doesn't help but all this talk about CRI and making things look more alive... I'm not getting it.
In all fairness, I have grown up under the light of cool white fluorescent lights so perhaps 6500k is my "normal" as opposed to most others who have fond memories of bedtime stories under incandescent or even candle lighting. I know I've had this argument with past roommates who complain my room is too bright as I complain that they keep the dining room too dark and orange and the sleepiness kills my appetite.
Whatever it is, this orange light really isn't doing it for me.
Other than that, my other complaint is that the light does get hot faster than the mh20. I didn't do a scientific assessment on how many degrees and how much faster than the mh20 but I guess I was expecting something more from the praises I read about regarding thermal management in this light. The funny thing is, the whole light warms up as opposed to just the head on the mh20. I know I read that somewhere also and yes that speaks volumes about the engineering that went into this light. In hindsight, (and before the flaming starts, please keep in mind I'm still quite a newb at flashlights) I suppose the engineers of ALL these lights are smart enough to not let their product overheat to the point where they damage themselves. My mind is still in the era of those hondas where the solder on the main fuel relay would melt and resolder themselves after decades of use.
OKAY, now, after all this complaining, I still think this is an awesome light.
There UI is definitely not as cryptic as I originally thought it was. Seriously, that review by mhanlen was probably the best I've seen of this light and he and some others have explained it in so may other ways too but its not that hard once you have it in your hand
It's much better than having to scroll through a billion different brightnesses and having a direct shortcut to high, med, and low is all I really ever need.
As for size, it is definitely smaller than the mh20 and it feels somewhat more solid/balanced in my hand than the mh20. Looking at the construction of the mk3 hi, it is obvious that they looked at every possible angle and made the light as small as physically possible for an 18650 light. I seriously wonder how thin that wall on the tailcap is. Also, much care was taken to make sure the mk3 hi doesn't accidentally turn on. The button is nested deep in the head just enough to prevent anything foreign from turning it on.
Anyhow, just sharing my thoughts on my new light. Hopefully, this orangy tint is just a phase or its something that shows it's true meaning outdoors more than the little 120 sqft room i'm renting.