I agree with Pat, pitted cones are the root of all evil. Getting replacement cones of the same type from Shimano can be a drag, but as long as the thread is the same, most cones will work. The seal may not be as good, and you may have to ditch the rubber ring to make them fit, but they will work.
Good quality cones are much better than cheapo ones.

With quality hardened steel cones, how deep does the hardening go. I know with some engineering components, if you file or machine away at the surface you reveal the softer metal below.