If OpenVDB/volume materials are coming soon, then there less need for that feature.
Artifact wasn't the best choice to describe the problem, but I didn't come up with a better one.
In the cloud, on the top side, there are visible displaced polys/small bumps where especially the sides of the bumps are often (fully) colored by the volume and the fade out only visible on the top of the bump. This leaves "spikes" in the image, depending on the viewing angle.
The other, lower areas are completely opaque, whereas a real cloud would have at least some fade to 0 for every area.
The latter is the bigger problem when using displacement.
It takes some time to tweak the settings to minimize it to the small spikes problem etc.
The picture shows the tweaked values. I could increase the distance, but then it'd lose its definition or give out something that looks cut off.
However, it would still be useful for things, such as an atmosphere for planets.
The absorption distance controls the density and the fade out could be used to fade it out.
Instead of a unit value, it should use a relative one.
btw, how would you convert a Vray material that has Fade-out radius enabled?
edit: bad example, look at the second exaggerated picture.