OK, the QTC, as some others have mentioned, is a little "jumpy." Especially from what I would call a "medium" to a high, there is very little incremental increase. Evena very careful turn causes it to jump to "high." HOWEVER, this light will be used nearly exclusively for "low" and "medium" so it really isn't a concern. The ludicrous insanely super-duper low is awesome. It is easily significantly dimmer than ultra low on an HDS light. I love that. there are two or three discernable "steps" (not really steps, just the smallest turn possible) up to moonlight on a quark. I love it. LOVE IT. Then, an easily "feelable" level of turn to a low-medium, and medium. Use the light all around the house last night, and couldn't stop fiddling with it. While it is longer than the Arc-AAA I have used and loved for years, I knew that going in. I'll give it a week or so on the keychain (with the Arc-AAA there as "backup) to prove itself....but I think I have a new keychain light for the first time in a LONG time.