It isn't derogatory but it is still quite commonly used or at the very least very commonly known. It is a very 'okker' term i.e. typically 'Aussie' and not the kind of term you'd hear used seriously by most people in urban areas. I guess you could call it lower class but if we're sucking up to our Australian-ness, you'd hear it being used in jest.
It is definitely usable here, I think...I know a few older Sheilas, it is just super super dated.