In answer to the original question, 10 lumens is more than enough to navigate by at pedestrian speeds. I've gone through lava tubes with less, and done just fine. If you have to run for your life, maybe not so much. When I had to run, and I wasn't concerned with becoming a beacon for a set of crosshairs, 50 or 60 lumens was pretty much necessary.

In other words, to find the privvy at elk camp at midnight, a small led light such as what DR puts in his pocket survival kit is acceptable. For making a bunker run during a mortar attack at 2:00 am when the generator has quit (again), a G5 Nitrolon was highly desirable.

I wish I'd gone the extra $12.00 and gotten the Fenix L2D Premium, but I'm happy with the Fenix L2D CE. I probably would have bought the Premium had I noticed it. The Fenix Store Site is a little whack to navigate.

The Fenix has taken the place of my Pelican M6 2330, which is now relegated to a backup light for similar reasons as your Surefire.

Agreed. It's also about enough for me to read by. Generally, the darker it is, the less light you need, because your eyes adapt.

I am a bit surprised by this. It's good to have 1 lumen or 10 lumens available when that is enough light, in order to avoid disturbing other people, ruining your night vision more than you need, and to get extended battery life. It's also good to have 120 lumen available for when 10 isn't enough - which it sometimes isn't. A general-purpose survival light should have at least 3 levels, in my opinion.

As for UI, that's one of the things which distinguishes a well-designed light from the others. I have an old Surefire U2, where you just twist the bracelet to one of 6 positions. The Photo Freedom is pretty good, too: press and hold to start dim and ramp up to bright continuously, release at the level you want; click to get bright, then press and hold to dim down and again release when it's at the level you want.