I have keychained a D25A Ti Nichia 219 for almost a year. It makes my keys huge, it's actually too big to really be a good keychain light, but I do it anyway because it's such a GREAT 1xAA light. Besides, I almost always carry my keys in my bag, not my pocket... so it's all good.
I have the 2014 model, I bought it shortly after they came out. It has 4 problems, all minor and none of them "deal breakers". It has no "moonlight" mode when using 14500, so I power it with an Eneloop Pro instead. It has the "blue ring" on the outer edge of the beam, caused by the anti-reflective coating on the glass. I don't notice this unless I'm intentionally looking for it. The "moonlight" mode is a bit too high for such a mode, seems like 2 or 3 Lumens - just barely on the edge of acceptible (for my needs). I wish it were about half as bright. Finally, there is no difference between "high" and "turbo" mode brightness when using 14500, another problem that is solved by me using an Eneloop Pro to power it. I do not know if these 4 problems have been solved in the 2015 version, but it doesn't matter to me. All of these problems are so minor when considering the level of TRUE GREATNESS that the rest of this light represents.
The bottom line? This is an AWESOME 1xAA Eneloop light, and a pretty good 1x14500 light if you don't need moonlight mode.
I highly recommend it, despite the warts.