The V20C was one of the real problem ones, but the V10A, V10R, V20A, V20R, all those i have played with (same head/driver in all of them) and the current models have the smoothest most perfect ramping profile IMO. Its perfectly visually linear (i.e actual output is exponential) and it goes low enough, and certainly high enough, especially on chemistries above 2v.
We have all bought too many lights, but the torches I actually grab off the shelf constitute the following;
For going out, medium compact size
- D10
- V10R
For slightly more power/or capacity
- Armytek Predator (for throw)
- V10R Ti 18650 (for compact with capacity)
- 120P 18650 (for flood)
For more power/size
- V60C
These make up 9/10 of what I would bring along. SO essentially, for All of my torch needs, a sunwayman V series plays a very important role, covering the compact, to the powerhouse. Essentially its the UI that makes this torch work for me, from the low to the high, and I find it super easy to achieve any level I'm after. I have never had the V20C, but all the other V series models don't seem require any sort of precision at all. I'm comfortable working with fine hand work, and maybe thats why I find it easy?
The ring is smooth, and friction is based on a Very thick grease. as long as the grease doesn't get washed out, friction will be maintained.
So with this in mind, I wouldn't really want to get it under solvents too often, however there is no reason for it to stop functioning, it might just feel different. Reliability wise, I don't worry at all, its a well built torch, and the driver looks to be well designed. Nothing under normal use will cause problems with the magnetic ring, I mean, magnetic switching is the best possible way to be controlling brightness, its the ideal non-contact way of providing an analogue adjustment with no mechanical points of failure. Just don't let the magnets get beyond finger burning temperature to risk demagnetisation (80 deg C?), which we under normal circumstances will Never achieve. I only demagnetised mine because I had it under the blowtorch ;)