Another light oft overlooked is the Inova Bolt 2AA. Not the brightest in the bunch, ours have yet to fail on us with daily use on a bike for over a year and a half.
i've been wondering about the L2D and E20. I keep hearing that you can use AA's in them that wont work in most other things because of the low voltage. What is the voltage cut-off for these lights where they start to dim?
I haven't tried all the lights available - but my Fenix L2D seems like a good 2 x AA flashlight. It runs for about 10 hours on medium, which is a decent light output for general use. On full output it will still run for a couple of hours and is very bright. 4 power outputs + strobe + SOS, well made - it would be a good choice and I got mine for under $70.