I have a brand new one I will sell you for what I paid. Good gun, just bought a spare as the price was right.
To answer your question, they spray oil and water based finishes (stains, polys, lacquers, etc) but they do not do very well at spraying latex paints. You have to get bigger needles, thin the paint 20 to 30 percent, and add floetrol to even get it to work decently.
As for WW finishes, I have sprayed waterbased lacquer, oil poly, and a few other things with excellent results. Paint I have personally had ZERO success with.