Apparently it’s more or less useful depending on the background. You might need to tweak the intensity to see the dust spots against a highly textured background. For example, here’s a sky from a Play Raw image, before and after:
I guess the important thing is to find some way to accentuate the slight contrast difference of the dust spot and / or its edge. Maybe another tool might do that. Or if there’s some way to find circular low-contrast features… but I don’t know of anything like that in ART.
Maybe an alternate strategy might be to do this in an editor that supports layers? You could probably use an extreme USM layer to expose the spots, then use that layer mostly transparent as a guide to find and clone them out.