I went from a Photon to an Arc, to the L0P, to the CR2 Ion (and sometimes Jil Intelli). Personally I prefer CR2 based keychain lights now, because even though they're fat (shorter, but fatter), I prefer this form factor because IMO you have more options to go with. Meaning brighter LEDs, bigger reflectors, etc.
If I were to go back to a AAA light however, I'd probably forgo the L0P entirely and go back to an Arc, although I might instead go with a Millermodded Arc rather than the stock one.
I say this because my keychain light is usually not my primary light, but rather a secondary/backup light, and the L0P is vastly inferior to the Arc in that regard, IMO. I can get many, many hours with my CR2 Ion on low, or a minium of several hours with my Jil Intelli. The Arc will last for several hours as well. The L0P however only gives around an hour, give or take, of good light. Not what you want in a back-up.
If you plan on using it as your only light, the L0P is OK, just feed it with NiMH rechargables. Even then, I'd still personally prefer a multi-level CR2 light like the Intelli because of how versitile it is (many hours on low, and very bright on high).