Can you post an example of the type of artifact you are seeing? Are you talking about how it takes too many steps to look good up close, and you can see ‘ripples’ in the parallax?
If so I have been thinking about how to improve that. My initial idea of going back to the sphere ray tracer did not work so well. I did try another attempt using Temporal AA to offset the number of steps a bit. shows very promising results for not much cost.
Before (showing the bad ripples with 48 as max steps and 8 as minsteps):
Using TemporalAA to randomly increase the number of rays by 1.2x:
You can still see a bit of noise where the artifacts were the strongest, but that is only after letting the camera sit still. In motion it looks pretty good.
Material nodes:
The results are actually about the same whether using 0.8 or 1.2 as the TempAA multiplier so its not all about the step increase (although 1.2 does look slightly sharper). Getting the steps to jump around causes the ripples to be out of phase with eachother. Increasing the number of steps by 1.2x does not reduce the ripple artifacts by much, they just get 20% smaller.