I'm mostly AA, but I like my CR123 lights too much to banish them to a drawer. In fact, my MSR Miox takes CR123s as well, so I'm actually closer to CR123s as a standard than AAs. I'm a flashlight nut, so I want my 230 lumen/ 2 cell/1.5 hour regulated light with me, or my 8 hour/80 lumens. I can't get that from AA's.

CR123s have the advantage of being better for cold, and have the ability for more output, and are great for storing longer term. I also like that 2 of them fit nicely in a waterproof matchcase with a foam buffer. They can also be found for 1.25-1.50 per cell if you don't buy retail, and buy a few at a time.