Hi list:
Under debian/xorg nv driver I had problem showing some graphics,
specially the ones that had color gradients, the steps of the gradient
were very noticeable and the same graphic showed much better under OSX.
Playing with the 'nv' options I found that using
Option "FPDither" "true"
in the 'device' section made a big difference.
If you are having the same 'problem' hope this helps you.
A. Corbi.