Just my take on it from selling them in the hardware store. Personally I wouldn't bother. As I said I sold them and we got around a 60% return rate for varying reasons. I think the return rate was so bad the owners told buying not to restock them.
I upgraded my AA and 2 + 3 cell maglites a couple of years ago with LED conversions. Afraid I cant remember the name for the larger torches - think it was the Terralux conversion, but I'm well satisfied. I used the Niteize II conversion for the AA which is much better than the original kit.
Fully appreciate that there are better torches out there now, but I like my maglites and they suit my needs.
Another voite for the terralux, i had a niteize led replacement, but it was low power and not very good build quaity, they may have improved design. I do use the niteize accessories, i have loads of stuff for maglite, bulbs, holders, headbands, lenses, pouches, thats why i keep with a maglite, and they fit the vertical holders on a response pack nicely. and if the casing gets damaged or worn, cheap to replace.
Yeah the nite-ize IQ Switch in conjunction with a terralux conversion works well IMO, I have a number of the Nite-Ize accessories as well. I have one of the bigger maglites, but haven't had a chance/time/money to do something funky with it. I will get around to it at some stage though.
I use the strobe mode combined with the glow wand as a safety marker.
There are some absolutely fantastic mods for the larger maglite models, on the smaller versions though i honestly wouldn't bother.
The upgrades themselves aren't often bad, but the artefacts from the beam after are terrible.
I've tried several maglite upgrade and to be honest they're simply not worth it.
Keep your maglites as back up's around the house, if you want or need a better quality light then buy one, it's just not worth the time, effort or money upgrading them though.
£12 for a drop in bulb from eBay? Not much money. No effort and gives you a torch worth using.
Beam pattern full of artifacts? I only want to light something up, why do I care about artifacts?
If you "only want to light something up" why would you waste money on a upgrade it in the first place?
To answer your question though:
Artefacts are dark circles within the beam of the torch.
This matters because if the thing you are trying to light up is in a dark section then the torch is not doing it's job, the "upgraded" maglite has EXTENSIVE artefacts.
If you have no choice you can "work around" these artefacts, but as you can buy better torches for the same money as the "upgrade" (or very little more in the case of the LD01) why waste your money on something not as good.
Here's the maglite upgrade at 200 lumens. Marks are from a scratched lens as far as I can tell. Focusing gives different beam patterns. Are the rings you refer to the artifacts? Either way it's a way better torch than it was before the upgrade.
£12 for a drop in bulb from eBay? Not much money. No effort and gives you a torch worth using.