On the whole, I've seen no failures with the CR123s (primaries) in a C-LE (older model with hidden mide).
I had one a while back with hidden mode, I tried out with CR123s. I only used it briefly for fear of burning it out. No problems, but I didn't get good contact so decided to just stick to AAs.
Others have used 14500s successfully, but many have burned out the boost circuit, so it can ONLY use 14500s. The newer ones (v1.2) will just fry so don't try those.
Overall, you're pretty safe with CR123s. Personally I wouldn't bother. It is brighter, but I love the form factor as is and I would rather not risk it.
Hmmm, not sure if that helped...
:sick2: