Here is description of mypaint.
Mypaint is a fast and easy/simple painter app focused on the painter, so you can only focus on the art and not the program itself. Currently MyPaint does not have a layer system, also mypaint is using pygtk with C extensions.
One of the interesting feature is that the width of the brush increse\’s with the speed of the stroke.
My personal experience with the application was that the appllication does not have too many functionalities but is really very easy to use. Just select the brush and use it after invoking it. Here are some examples of the kind of effects that you can see with mypaint.
On the right hand side is the toolbar for selecting the brush and the effect is displayed with the brush selected. Quite simple to use.
Watch out for some more screen-shots in coming days.