I've used it for metals, plastics, PVC (Reaper Bones and stripping the primer from Nolzur's Marvelous Miniatures) without any problems. I also used it to strip the paint from a metal toy car, which it did really well

I haven't had problems with anything I've thrown at it, and I've left some pieces in for several days.
However, I don't think I've tried anything that had greenstuff on it. I feel I must have used it on plastic figures I've glued together, but I'm struggling to bring an example to mind.