It would be nice to get a more intelligent fill tool. Here's a comparison with PaintTool Sai. The fill tool in Sai works well with thin lines and thicker, soft lines. It still sort of works on very thick lines with a lot of gradation. Rebelle's fill tool wasn't able to fill the area defined by the thin lines without flooding the entire canvas, even with Tolerance at 0. If I patch up the very thin and light part of the line, it does fill, but the result is not smooth and there's still a small gap all around. Rebelle's fill tool doesn't handle the softer lines well at all.
