Getting hit with 400+ lumens at night creates a universal reaction. When spotted in the eyes, it can take up to a minute to recover. I've also never seen a person who's immediate reaction wasn't to turn away. It's really a great defensive tool under some circumstances.
I have a few lights for work but don't EDC a light. I should, but after carrying around 20 pounds of stuff on me at work I look forward to having just a small pistol, knife, cell phone, keys, and a wallet.
Elzetta makes some good stuff. Surefire is quality, but they're a few years behind in brightness compared to everyone else. CR123 batteries are a monopoly too. Most of my light use is a 450 lumen 3.5 million candlepower spotlight since it's rechargable. You can get some insanely bright Chinese flashlights with rechargable batteries that are cheaper, brighter, and longer lasting than CR123's too. Sad to say, the most advancement in flashlights lately has come from China. Brands like 4Sevens, Klarus, Sunwayman, and Nitecore make some pretty insane flashlights and Surefire's only selling point anymore is that it's US made and arguably more durable.