I can not say enough good things about the X1.
It is a light for very specific purposes and if you try to push it outside it's 'design envelope' you will be dissatisfied. On the other hand, if you need a tight spot with no spill, tiny form factor, good battery life, and good throw in a 1AA light under $20, you can't go wrong.
My wife has a wide list of specialties in technical theatre. I did too, for years. She wanted a new work light and we talked over her requirements. They were very much like mine were. In theatre I was always looking for less spill. The less, the better. It is very important to not disturb or distract people any more than you have to. I carried a series of mini-magzillas. If I were doing it now, an X1 could replace the MM for every task that I needed it for, without a doubt. YMMV. In my case, it would replace the MM and I would have a light with a smaller size, no spill and quite a bit cheaper to feed. I would slide a little clear vinyl tube over the tail-cap (just as I did with the MMs) so I could hold it in my teeth.
Comparing it to the fine ARC-AA is like apples and oranges. You'll see.
I got one for my wife and I thought it would be a win, win situation -- if she didn't like it, I'd get to keep it. Fat chance. She loves it. As previously mentioned, she reports that the WOW factor is pretty strong as far as the uninitiated are concerned.
It is a very specialized light and if you need what it's got you'll be very happy. If you want it to find your way down a bushy path to an outhouse at night without poking your eye out -- you'll be very disappointed.
Let us know what you think of it.