I think we should create a thread for that,- something like post your "what would you create as a CS4 panel...." with lots of GUI sketches and ideas about custom panels- and sharing resources.
A kind of "lazy mouse" feature for the brush would be nice. Other apps like Zbrush let the user turn on a lazy mouse feature that smooths out brush motions over a certain pixel distance. When the person draws the actual drawing cursor drags behind it in a smoothed motion. This would make drawing curves really easy and with…