In "Rose Jacket" I left a lot of the initial underpainting visible as an interesting contrast to the thickly-layered paint in the woman's jacket and in the light background. I like the way that the untouched single layer of darks on the right and in the skirt appear flat in comparison to the dimensional feeling of the rest of the figure. Had I refined these areas with another layer or two, I think I would have sacrificed a lot of interest though I would have created more believable form.
Not every painting gets to keep this much underpainting, but I do try. Some end up with a second layer everywhere because, as we all know, every painting has its own path.