I just bought artrage and every feature is just dead-on. Everything is so well thought out! This is all very very addictive. Great work!
But i do have a suggestion.
I love that you are able to rotate the canvas, a feature that lacks in most other drawing applications. I think it would be even more usefull when you also have a key to toggle rotating while holding down the key and returning to you previous tool. A sort of quick-rotate just like the move tool works.
Again great, great work people!