UPDATE: February 20th, 2012, Version 2 officially finished
UPDATE 02: Added Pressure Stabilizer 'modifiers to the Airbrush and Soft Eraser tools. Airbrush is set at '9' and Soft Eraser at '6'
UPDATE 03: Replaced the Marker with an awesome Watercolour tool.
***I also use the Blur tool quite a bit for some things now with Blending and "Keep Opacity' unchecked, and all other settings at 100% except Min Density which is kept at 0.
It took a while to get exactly what I wanted but this is the set-up and settings that I settled on for Paint Tool Sai. With its great canvas rotation I discovered that colouring was much more comfortable than with PS so almost my entire process has been moved over to Sai. Unfortunately the lack of manipulation tools and assorted other functions that Photoshop has stops this from being the ultimate art program for me (especially the fact that I can't stand its Pen tool, which I use a lot in PS) so many things are still left to Photoshop.
I'm finding ways around it, but to have everything I want all in one program would be the ideal dream.
Seriously though, whoa this thing is huge. Hopefully I won't find a need to update it again for a loooooooooong time.