The kind of blurring that PorcupineFloyd is talking about is above and beyond any of the options that the cloud layer already provides. By blurring in image space you can further eliminate noise without increasing render times so it's a useful technique. The problems is that it loses detail and blurs the edges of clouds, but often this is perfectly acceptable (especially on high res images where there are more than enough pixels for the clouds). Being able to do this in the renderer would help in situtations where post blurring can't be used because of objects visible behind and through the clouds.
At some point in the future we may need to separate the atmosphere/cloud rendering pass from the surface rendering pass, and if we do that then a blurring option would be much easier to implement.
Matt
