Just downloaded SketchBook Express from AutoDesk, a free App on the Mac App Store. I don’t have a stylus or a drawing tablet at my desk so I gave it a try with the ‘ol mouse and sketched up a quick concept car. Not bad for a free App, although it’s buggy on my Mac Pro, some of the options, such as selecting brush opacity and angle from the selector puck are not working as they should be. It also appears that you’re limited to the number of Layers. I could really get into using this for some fine art fun, just need to get myself a stylus and drawing tablet. Give it a try, I think you’ll like it!