It's maybe a little old-fashioned, but honestly, I haven't seen
Joy enough at all to figure out where I think it "fits." It doesn't seem like
Faith,
Grace, etc. to me despite the obvious connection; it isn't nearly as popular to my experience. That lack of popularity definitely makes it more sweet and interesting than its tired counterparts.
I know one
Joy. It suited her and didn't seem out of place in any sense.
I get the feeling that it might be a more common middle name than first, certainly, but offhand I can't think of anyone I've met who has it. It's like
Mae or
Lynn in that it's the kind of thing that we tend to talk up on this board as 'refreshing' first names or whatnot but that don't seem to make actual appearances as such, here or otherwise.