YMMV, but I used to use my Ultra G to drain out my used AAs before, and one day the bezel was very very difficult to turn off. I had a lot of difficulty unscrewing it, but finally managed to, and still had to pull hard to get the bezel apart, with a loud 'pop'. Turns out that the used battery had leaked and probably caused a gas buildup inside. Now my Ultra G has a blotch along the side down to the -ve contact. Had to scrub it out before it was usable again. /ubbthreads/images/graemlins/frown.gif
Don't know if it was a one off thing that made it so (mind you it was a Duracell), but just thought I'd let you guys know anyway.
With 123s I use my Tektite Splashlite Led and its holding up really really well so far. Cells that are too weak to power up my KL1 and Arc LSL still put out a decent amount of light in my Splashlite Led. Definitely a good choice!!
MilkyCandles are the best from what I've heard, but yes, they work on 123s only. I heard that MilkySpit is planning another run soon, I think, so keep your eyes open!