They were fashionable when I was a young teen - with an oversized chequered, flannel shirt worn open over the top. I never had one.
But I just saw some in a catalogue, and thought "Ooh, those would be just the thing to keep my back warm in cold weather." 
So...has/does anyone wear them?
Are they uncomfortable? (I'm concerned about their potential to give you a wedgie, especially if you bend down)
Are you supposed to wear pants underneath them?
I'd be wearing it as a vest, so not bothered if they are a huge fashion faux-pas, as it would be out of sight anyway.