I've seen them once in my life, in Smoky Mountains, about 10 years ago. It was pretty much spiritual experience. The darkness came alive. I cried when I saw their luciferase smeared over windshield and glowing long after the creature was dead. I knew lots of lore about them, saw them in mass culture - never realizing I never saw one myself, even though I take care to notice all living things around, from bacteria and yeast to mycchorizal networks.
I live in Europe.