Actually I DID purchase the TK10 and several CR123 pairs from batteryjunction.com. The shrink-wrapping of the CR123 is a pretty cool idea.

One of the things I like about the TK10 is that the rear switch is simply an on-off button switch (you can hold in in lightly to temporarily turn it on too). I can rotate the rear of the light a bit to prevent the switch from accidently turning on in a bag/pack. The selection of high vs. low light level is done by rotating the front of the light (the capsule holding the LED).

We use a single CR123 Fenix P1B attached to our barn key - along with a Storm whistle - so that we have a tough & bright light when out in the barn (used to look for horses, barn cats, and scarey monsters hiding in the dark). The P1B is turned on/off by rotating the front of the light. The problem is that the same rotating switch is used to cycle through medium-high-low-flash-SOS settings, which is kind of a pain. Its also hard to do one-handed.

BTW, the Fenix P1B has been uber tough, goignon its second year on a VERY abused keychain. We've previously gone through several single battery Maglites that each fell apart. The P1B's paint is pretty scratched & chipped, but it still works as well as the first day we got it. I'm counting on the TK10 to be just as tough.

Ken