Our experience is varied
We rent out holiday accommodation.
Last year Google Adwords worked, not wonderfully but about on level with the cut Booking.com takes. This year it was a loss.
FB has not given a single booking so far, but worked when advertising for cleaners.
To me it is scary that some small companies rely on FB for their web presence. No website, just a FB page.
On a personal level, I just don't get FB. The interface is a royal mess, I can never find anything. Which is also why my contribution is very limited (but organising things with other parents just don't happen without it).