I only use lithium primary batteries and high-quality rechargeables.

The E01 is bullet proof and I have them stashed in kits, but for about the same money the Thrunite Ti has more runtime on low and a heck of a lot more light on high. The E01 also has a nasty purple tint. Until something better comes along at that price point, the Ti is what I suggest to folks.

I keep a Preon ReVO on my keychain, so I don't need a Photon-type light. I buy fauxtons from DX ten at a time and give them away to people.