What are my best battery options for this light 2x14500 or something better?
As everybody else has already mentioned, you can't do that. 2xAA Eneloops work quite well. But really, the best way to run it IMHO is with the 1xAA body and a 14500. A little brighter than the 2xEneloop config, and even if you find yourself with a depleted 14500, it runs pretty well on a single AA alkaline or Eneloop. Not near as much output as the high-power configs, but all modes work, and are usefully bright.
How do you guys like this light overall? opinions please
One of my favorite 1xAA lights, since I more often want flood in that size light, which is a good thing because these small XM-L lights don't throw worth a darn. I have an original Quark AA² Tactical R2 that out-throws it handily, and a $22 Balder SE-1 in R5 that out-throws 'em both.