I like SketchBook Pro very much for the purpose of rough sketching, layouts, storyboarding and generally creating the inital basic artwork which I then later use to import into other programs such as Illustrator, Painter or Photoshop for further coloring or line-art inking.
Sometimes I lay down some color in the sketches/concepts/layouts directly in SketchBook. It has some very useful coloring tools such as the advertising markers and airbrush.
Digital Pencil Cartoon Sketch in Autodesk SketchBook Pro
