>Anyone used one?
I only used ones for small business (brother), they aren't made to be safely refilled, but you can do it yourself. I suppose that those who are to be refilled can be done without buying a paint suite and a mask.
It's worth it in terms of savings, the cost of buying toner instead of cartridges is divided by 20. Instead of a 0.10 cent a page it's 0.01 cent. The maintenance of the printer is what cost most after doing that.