I think it's great, but the one thing I found myself wanting more than anything was an eyedropper tool. it would be very helpful in maintaining a consistent color palette while experimenting.
Another idea is to download a randomized color palette, and have that be a module that sets the color for each stroke. Could download the palette off the web from someplace like this: http://www.colourlovers.com/palettes
One last minor gripe; I don't really like the default color picker (the square one.) I don't think it represents colors in an artist-friendly way. You can't pick a desaturated dark color, for example. I know you can go to the second color picker to do this, but it seems a little weird.



