I've had experience or second-hand knowledge with three variations; OpaLec Newbeam (2), InReTech (2), and TerraLux (1).
Both InReTechs broke a piece of the "crystal" off when dropped, rendering the light unusable. InReTech did replace the crystal free of charge when requested, but when it happened the second time I wrote the unit off. The TerraLux, owned by a friend, also failed less than two weeks after he got it. I don't remember exactly what broke, but I can find out if its important to you.
The OpaLecs are going strong. The first one has been on my work bench for a couple of years now; it gets used daily, and dropped at least twice a week. Actually, lest you think I'm terribly clumsy, it gets knocked off the bench as I move stuff around. My brother has one that sees similar usage/abuse. My pal with the TerraLux replaced it with an OpaLec, and it is now his FAA-mandated flight bag light (he's an airline pilot). And, my second one rides in the warbag as a spare.
The point is, the OpaLecs have stood up to normal "wear and tear" through being used; the other two brands have not. Sure, that is a very limited sample. But I think you'll find more OpaLecs in use, by satisfied users, than any of the others.
The OpaLec's regulation provides ten or so hours of medium-bright light. In absolute darkness it would be a great primary light. Very few of us ever see conditions of absolute darkness. The OpaLec excels as a utility light for peering into dark places around the office or home or vehicle. It will not light up the back yard, but is plenty bright enough to handle probably 90% of what a domestic flashlight is normally used for.
If you want super brightness, there are plenty of "mods" around for that, although, to me anyway, doing this on a Mini-Mag is somewhat akin to polishing a turd. If you want a very bright small light, get a SureFire incan.
The concept of an LED mod for the Mini-Mag is an excellent one. IMO, the OpaLec NewBeam is the best bang for the buck in that genre.
But look at the StreamLight Lux Jr too, as was mentioned above. It is only a few bucks more than a "conversion", and already has a clickie switch (which is very handy and makes one-hand operation a snap. Both of my OpaLecs have Kroll tail-cap clickies- another $5).
You can pay over $50 for one of the "premier sandwiches". Or, you can pay a trifle more and get an OpaLec conversion or StreamLight Lux Jr. AND a SureFire G2. The G2 is The Great Equalizer among utility lights; everybody should have at least one... /ubbthreads/images/graemlins/grin.gif