[john.gersh]

Interestingly, OG for the iPad has a freehand tool for drawing shapes and a corresponding marker fill style. The shapes look hand-drawn and the fill style looks like the shape was filled with broad marker strokes. It also has a hand-drawn line stye, though that's more like a pencil than a brush. See the example at http://www.omnigroup.com/products/omnigraffle-ipad/

Maybe they'll migrate to the Mac version at some point.