I like it but want it done well.
1A charging
USB-C
Indication of what the current voltage level is
Ability to use the light on low (above moonlight) while charging
For me any cons of built-in charging are far outweighed by the sheer convenience (USB-C especially). Especially soda can or bigger lights.
There are more than a few widely disparate variables with this issue, so I have not yet made up my mind. Therefore, I go for the variety effect. Some of my lights have it, and some don't. I like reading other peoples' opinions on this issue, because my opinions are not very valuable.
They have their place. If they are too slow, I don’t like them. If they are way under one amp for the bulk of an 18650 charging it’s too slow. Micro USB needs to go away. Type-C or magnetic is ok. If lights are going to come with batteries that have built-in charging then they need to have dual springs and be able to use regular length batteries. Lights that I carry on a regular basis need to be able to go under water. Type-C can be made to be waterproof without a rubber flap. EDIT. There’s no reason to go through with the test because I can see in around the type C port. Within the next few days I’m going to put a Wurkkos fc11 under two feet of water without the flap in place and see what happens. I’m going to put it under for 10 minutes while off. I’ll then run it for 10 minutes after removing it from the water. And then a day later I’ll put it under for 10 minutes while on. Actually I’ll do the test with two lights at the same time, one with the flap open and one with the flap closed.
This right here
I don’t mind it on larger lights but definitely don’t want it on smaller lights. I have three lights with USB charging, Wurkos TS21, Nitecore MH12GTS and MH20. I know the MH12GTS charging port is waterproof and I’ve got the MH20 wet before and haven’t had issues. All of the port covers are nice and secure and really don’t see the issue that people have with them. I’ve had them all for a while, (both the Nitecores for years) and still have the original covers on them.
In general I don’t like the built in chargers. My tool lights definitely need ultimate water proofing. Toy lights it’s not an issue. Chargers came be made for water proof work lights. IMALENT MS06 charging port is an excellent example as are the Streamlight Stinger.
For an EDC, it’s a huge huge plus. I used to “top off” when on a bus and could put that time to good use. The port’s there, so why not use it? Same with a car-charger, ’puter usb port, powerbank, anywhere. No need to carry even a small charger for that.
Specialty lights, might come in handy, but things like diving lights, probably not a good idea.
“Bulk” of a charger? Have a look at the MH20. Most compact 18650 light I got, and it’s got onboard charging. Most chargers nowaways add so little extra length/volume as to be negligible.
Multicell lights (parallel), it’s almost a must. While I much much much prefer the Q8 with its warmer floodier beam, I kinda shelved it for my DC7, which has onboard charging, and suffer through a cooler pointier beam. It’s just a pain in the ass to charge a Q8.
All anyone needs to do is charge a cell once in a particular light, then immediately test the cell’s voltage once it “goes from red to green”, and make sure it doesn’t overcharge. Then let it cook a while to make sure it doesn’t keep charging.
Yes, it’s a convenient feature. I find recharging essential for lights that are going to be a gift.
I’m a lazy bone, I think it would be better to charge the flashlight directly.
When I’m reviewing, it depends on who the light is aimed at. If it is aimed at consumers, then built in charging is usually a must, if the light is aimed at enthusiasts or people who understand Li-ion safety, then charging is not a must.
I agree with Stephen, I would get built in charging for my mom but wouldn’t get it for myself.
Time will only tell Manker’s approach of having two battery options vs Acebeam proprietary approach (ie X50).
Interestingly, the yes votes are leading. If this poll had been out 5 years ago I think it would be reversed. Opinions slowly change.
I think the demographic has changed over the years. In the past on this forum in particular a lot of users took a “budget light” 
and modified to suit their likes. It seems now a lot of users aren’t interested in that stuff. Just give them the all-in-one perfect light with a perfect single emitter beam, boost driver with multiple leds for maximum efficiency, perfect cri to each individual eye, perfect UI with side button and 16 clicks to lockout, in light charging with battery level indicator, super moon to 3000 lumens slow ramping, unlimited long turbo, all in a package about the size of fw3a.
Did i take that too far 
That’s about right.
On my edc, no. Reason? It’s always on me unless I’m in bed, and when I need a charge, a battery swap is the way to go.
Rubber charging port covers all suck. Even designs like the K1 with the port in the threads isn’t that convenient, unless I’m traveling and can’t take loose spare cells or don’t want the bulk of a charger.
Induction/cradle charging would be nice imo for an edc, and magnetic connections like skilhunt uses would probably be second best. Something that doesn’t require the light to be broken into two pieces or have a vulnerable port+cover.
Onboard charging on multi cell or soda can lights is a yes for me though. These lights are already ‘toys’ most of the time, and it is nice to just top then off every once and a while or after the rare times I use them.
what I was referencing by the bulk chargING was the constant current period where the bulk of the charging is done. That’s before the current starts dropping off after it gets to 80 or 90%. The term bulk charging is more used in automotive, solar, rv and other larger battery stuff. I use a USB tester to watch any new light while charging and pretty much most of the time when I’m charging any of my lights or batteries. I had a new Wowtac, I think it was the a7 or A6, drop the current way down near the end and it was taking forever to shut-off. I pulled the battery and checked it and it was up at 4.25v. I put it back in and the indicator light was still red and it was pulling some very small number like 0.07 amps and against my better judgement I let it continue to see what was going to happen. It finally shut down at 4.3 volts. I watched it multiple times after that and it never went above 4.2v. I don’t know if the issue is related to a new battery or what was going on. Without a USB tester you don’t know what a light with on-board charging is doing.
Wellp, nowadays, charging circuits are compact, integrated, and almost error-free. Even 1% precision is considered “sloppy”, whereas before, 5% was good enough, and you’d need multiple trimpots, etc., to tweak cutoff voltages and the like.
So charging to at least 4.10V but never exceeding 4.20V is a small miracle in itself, with no trimpots, nor anyone needing to trim them on a per-device level.
So yeah, it’s definitely gotten “good enough” to throw ’em into practically every device that can benefit.
K, but I was referring to
when it came to “bulk”.
I bought a torch with built in charging which was not (what I consider) cheap tat with a usb hole in it.
Some models have magnetic charging pads so there’s no hole. But actually the one I got was from the Convoy BD series which clamps onto and charges through the switch which acts as two contacts… and still lets you use the switch while charging.
I hate holes in torches, rubber flaps, rubber button covers and I also hate scuffing o-rings taking batteries out just to charge and putting them back.
If you can charge the battery inside a torch without compromising the torch body it’s a huge convenience.
Everyone saying integrated charging has gotten “small enough” is carrying larger torches than me.
My collection is large enough that I have options with integrated charging and none of them get into the EDC rotation. An equivalent option that’s just a bit smaller always wins. If size didn’t matter much, I’d never carry my FW3A over my KR4. Maybe there’d be some 21700 lights getting pocket time.