There has been an infrequent problem due to some kind of internal tolerance problems where the light can go into intermittent activation.
My Gladius arrived the other day, so of course I was playing with it, using a set of batteries for familiarization with the switch. (Refamiliarization actually -- I had one before and returned it.) Someone came to the door, causing our pug dog to go berzerk. So I strobed her to get her to stop barking. I got about two strobes and nothing. Plan B: squirt gun. Back to the light. Punched the button again, nothing. Switched to constant on, nothing. Switched to momentary, got light. Variations on this will hapen when the tailcap is not on just right. It is repeatable, but it is not a frequent problem. I would say 1 out of every few hundred activations or less, and this with lights that have the problem. Not many do.
What happens is that there is some kind of glitchy contact (or something) on some lights that happens sometimes. You can lose light during activation, but there is an easy fix: remove and replace the tailcap. This causes the electronics to "reboot" and the light returns to normal activation.
The first light I had (a gray one) was returned for a fluke tailcap that leaked, but it too was intermittent. I lost confidence in the design and decided to wait until the tailcap was redesigned. I read in the Manufacturer's Corner on CPF that the cap issue had been fixed, so promptly ordered another one from Night-Ops ($206, not bad). Wouldn't you know it though, I purchased too early. The new, redesigned caps are not in wide circulation yet. So I await a fixed light as I type this.
Another thing to be aware of is that the tailcap can rattle. Some caps sound like there is a BB loose inside. The one I just sent back had a horrible rattle in constant on mode, nearly went back just for that. The old gray one just barely had a rattle.
The gray one's finish was ok, but not real durable. I would say it was about like regular black anodizing. I had it clipped to the front of my bunker coat for exactly 1 structure fire. It wasn't knocked around that bad, but did get some bare spots. A gray light with patches of aluminum doesn't look that bad, by the way.
So that's the long version.
It is a great light, just a glitch with the original tailcap design in a few lights.
Scott