The L4 is everything I hoped it would be and more. I was contemplating the purchase for almost a whole year! It's a great light and my favorite EDC.
I knew nothing about Surefire until last April, then I found CPF while researching another light. There were many L4 discussions and the more I read the more I felt it was the light for me. Bright LED, rugged construction, not to mention slick styling.
I love the L4 the way others love the A2. It is with me from the moment I wake up to when I go to bed and, though I know the A2 will prove more versatile in the long run (like reading directions at night on road trips) I can't imagine it or anything else replacing my L4. I was going to do the two-stage mod but have decided it is not necessary. If I want less light I use my bottle-cap diffuser. If I want even less light I'll use the A2.
My love for the L4 was solidified from day one, but if you find yourself unsure, give it a week or two. Take your dog on longer, darker walks. Explore dark hallways and closets. If you decide it's not for you, sell it here. If you're completely happy with it, buy a couple of AWs 17670 rechargeables. Then you'll make up for the cost of the light by saving on batteries. And if you find the 17670 doesn't fit your L4 (It's a gamble.) you just have to sand the inside of the tube. It's a little bit of work but worth it.
Good luck and congratulations on your purchase!