I have been looking for a simple program to entertain my daughter with drawing (she loves it) on a Mac. I've got a (cheap) Wacom tablet that wanted to employ as well. TuxPaint is nice, but I hate the rubber-stamp/clipart mentality it sort of forces one in (and sounds are annoying). Also, I think that interface is overloaded. Accidentally I cam across this marvel — and have bee having lots of fun myself!
It certainly is neither Photoshop, nor Illustrator — but it needs not be! The interface is extremely simple (if a little unclear at first, but this is really well taken care of by quickly skimming through a 14-page slide set of a manual), does not get in a way at all. You can pretty much scribble anything and layers are a great way of building up onion skins of a drawing. Tracing mode is great for when your treasure wants to use another picture as a model.
Here's a quick one, took no more than 10-15 minutes to scribble :)