A word to defend the people who convert old treadle tables into desks etc; while it is sad to think of it no longer being a sewing machine, I think that if a treadle stand/cabinet or machine table is otherwise destroyed, it is great that they are re-used, re-purposed, and given new life.
I don't think that all iron bases/cabinets-turned-home-decor should necessarily be milk-painted with the same brushes of disdain. ;-) I have seen a few (natural wood, oak, nicely refinished) that are tastefully done (read: not festooned with pumpkin and roses applique...), and I certainly think that this is a better thing than letting it rust as lawn decor, or go to scrap.
Just a thought.