I never liked the interface of artrage- ugly and non- productive in my eyes. Sai on the other hand nails it pretty well - super customizable and easy readable interface without any fancy effects or experiments that went wrong.
I have artrage and like it, but I much prefer a more customisable brush engine like sai and artweaver. I'm actually finding artweaver's brush interface much more intuitive than sai's, although there are a few clunky bits to artweaver that are getting in the way (switching brushes, changing bleed ammount, etc) many instead…