I EDC a Surefire E2D clipped in my left pocket. Primarily, I carry it for those times when I must absolutely see something clearly in the dark. Like in a shoot/don't shoot situation. I have its older cousin (a 6P IIRC) next to my bed for exactly the same reason.

I went out to Surefire's web site and purchased a plastic disk that holds a spare bulb and 4 spare batteries. I carry this in my "bag of tricks" that is usually within arms reach or in the car.

I have carried Surefire lights for many years, and they have never let me down. I understand their limitations (runtime, batteries) but use them for their intended purpose and use other lights when the situation dictates. There is no "perfect light", but one might argue that there are perfect lights for given situations.

Enjoy your new purchase!