Still, I wouldn’t want Ol’ Sparky strapped to my head, either.
I just picked up my very own D25S and like it quite a lot. Most of my impressions match the comments above, but here are some particulars that I found while testing it out on the property:
Reasonably lightweight. Even with an 18650 cell, it stays put on the strap even without a top strap. I did my very best version of “13 year old me at the Iron Maiden Powerslave tour concert in the ’80s” and it didn’t slip or slide to any degree that caused me to worry after banging my head for a bit.
The angle adjustment isn’t super grippy, but it makes it easy to fine tune and still doesn’t slip.
The hidden USB port is a design that I like and I hope more manufacturers give it a try because it most likely keeps out grit and moisture better than some of the rubber flap designs I’ve had and tried out. It won’t wear out and need replacing either. It could use a touch of lube on the o-ring though. That would make it even more weatherproof. It didn’t come with replacement o-rings. I wish it did because finding a particular one for a particular light can be a pain. Hopefully it’s a somewhat standard size and one that is shared with other lights I have.
The levels are spaced well. It wasn’t hard to find one that worked for up close stuff or reaching out into the darkness of the edges of the yard. I didn’t read up on the UI and it confused me why it sometimes went up in brightness and sometimes down. I’ve still got to read and play with it a little more, but regardless, it didn’t take long to scroll through the levels to find one that fit a given situation. A good UI for me is one that can be understood with a very short amount of fiddling. I’m sure some would be confused, but with a number of different UIs in my flashlight collection, I don’t mind if one is different, just so long that I can navigate it in a minute or less. A lower low might be nice for reading in a tent without keeping my wife up though.
The light is only available in CW tint which definitely isn’t my favorite. I’d bet that they sell more with that tint and by being able to report the added lumens compared to a NW or WW emitter. I’ll survive with it. These are my first SST40 lights and they do the job nicely. I’ll most likely compare them to my other lights in the near future, but they put out a nice beam with a hefty dose of spill around the diffused hot spot. I prefer really floody headlamps so I don’t have to actually look down to see my feet. I’ll check soon to see how these fare. I can’t recall from my evening of playing around. I wonder how a diffusing film would work…
I’m not so keen on the battery drain. The “manual” or “smaller than a business card” fact sheet warns to turn the cap “half a circle” to manually lock it out. With anything going in a backpack, I do this anyway. It may be a pain or a sorry surprise if people don’t follow this tip, but for the money, it’s something I’m willing to deal with. It’s nice that they decided to share this in the paperwork with the light. It comes with a Sofirn 18650 cell that from the length of it, appears to be a protected cell. It’s a nice pairing for a light that might drain the cell faster than others.
About the money side, 77Outdoor and their related partner company, Sofirn are top notch in the budget light range. I’ve got a handful of their lights and my family has some of them also once they played around with my lights. Yup, there’s plastic and only an IPX6 rating, but for the final touches, they seem to cost more from other companies. Overall, I’m liking this light quite a lot and it’ll come in handy for a lot of jobs in the shop, around the house and yard and even on the trail. I’m a strong believer that more people should own a headlamp. Having hands free and not having to bite a knurled aluminum tube are well worth the price of admission.
I didn’t have complaints about the strap(s) at first, but now I sorta do. Not a big deal, though.
The adjuster doesn’t stay in place, often loosens for no reason. Once it’s taut, it more or less stays in place, but sometimes when slinging it on, it just “opens up”.
That, and the plastic clips that hold the light also let me pull the light off the strap, instead of pulling the strap off my head. 
I like the kind of enclosed-loop rubber mount like on the RJ02s. Them’s built like a tank.
But yeah, the D25S is more conventional in the UI, and is nice and easy to figure out. The UI on the regular D25? I think I’m in the minority, one who doesn’t hate it, and in fact it kinda grew on me. Medium right-off, another click for brighter. The 2 most-used modes are right there and ready.