Control ring is my favorite interface for everyday use. Around the house, out and about on short trips, there's nothing like it. If all you've used is the click-click-doubledick-click our-engineers-aren't-even-trying-so-we-hope-you-accept-mediocrity interfaces, the ring is incredibly refreshing and wonderful to use. Best interface for plain ol' everyday use.
But I have a number of uses for which it isn't as well suited.
- For defensive use, I have to be able to guarantee the light will come on in high. Control rings can and do get turned in the pocket.
- For emergency/earthquake/BOB-gethome type use (e.g., I'm headed to SF for the evening, trip to LA with the kids, etc), the battery drain makes it unsuitable. I want lowest-low to be so efficient I can use it practically for free, etc.
- When I'm traveling super light and need a minimum-sized light, control ring adds where more length than needed
Right now, though I'm not exactly thrilled with the interface, a TN12 is both my defensive and travel/earthquake light, because once I lock it on high it stays there, moonlight can last for weeks, etc. There are other lights around now with better interfaces (I hate the head-twisty, sometimes the mode doesn't change and it's incredibly awkward regardless) and similar performance, though the TN12 is in "good enough" status with me.
But 80% of my actual flashlight use? I'll choose my control ring light, every time!