I like them because you can dunk them in water and they still work right away without messing with them. I made a video test of one compared to a bic and a butane lighter that is around here somewhere.
They can also tail stand very easily, and you don't have to hold down the gas lever to keep them lit like a bic. As far as how much fuel they carry, it is a decent amount, but it won't last forever. One of these days, I'll fill one up, light it, and see how long it goes just to see how much fire you can get out of it. All that said, I carry both a mini bic and a peanut lighter in my kit, along with a firesteel.