As usual, I will add the "incan" perspective on things:
The nice things about a filament is that as long as it is hot, it will radiate light: the current can be constantly reversing direction and going through zero (as in house lighting) or it can be turning on and off rapidly or it can be dead constant--it doesn't matter. All that matters is the power applied to the filament. As long as the variations in the current and voltage are fast when compared with the thermal mass of the filament, it doesn't matter.
This allows incan regulators to be very efficient. More efficient than constant current buck/boost LED drivers. Here is a link to
Willie Hunt's Lightbulb Regulators which are 99 percent efficient. He has some good comments on why regulators are important for incandescent lights.
The biggest reason is that an incan is most efficient and puts out the best light only within a narrow voltage range, which equates to a filament temperature. You want to be within 100 or 200 C of the melting point of the filament. No battery chemistry in the world has this kind of discharge curve, which means that for best incan performance a regulator is ESSENTIAL.
Plus, the LVR3's have a feature which slightly dims the light once a second when the battery voltage is getting low to warn you that you are towards the end of the run, plus there is a feature which automatically dims the light when the battery is nearly depleted, for extended low-level light, a "moon" mode if you will, just as with some LED drivers.
And also, the LVR regulators have a "soft-start" feature (as does the SF A2) which limits the starting inrush current to the filament, and increases the life of the filament as a result, because almost all blow outs happen when you first turn the light on.
Also, the LVR's have an optional low battery voltage cutoff to prevent you from damaging certain rechargeable battery chemistries which can not be safely discharged below a certain voltage.
All of this adds up to a significantly better light, and I wish that there were more regulated incans out there. To my knowledge the only production regulated incan is the SF A2, and it has to use the less efficient constant current regulation due to the presense of the LED's. Of course, you can buy lights with LVR's in them, but they couldn't be classified as "production" incan lights. Oh well. And it doesn't look as if SF plans to make any regulated incan versions of their lights for the future, either
How significant IS a regulated light? I'd say pretty significant, for all of the reasons I mentioned. Plus, I didn't even bring up multi-level brightness, but that's because I think the filament should be run at the optimal temp for best CCT and efficiency.
Hope this added something to the discussion. Errr, I mean something
helpful.
