Autodesk has released a configuration guide we put together for AutoCAD Isometrics.
http://docs.autodesk.com/PLNT3D/2014/ENU/De-mystifying%20AutoCAD%20Plant%203D%20Isometrics.pdf
About 80 pages long, the manual gives both an overview of the isoconfig.xml and some detailed examples for configuration.
One of the key features is a list of the skeys used, available symbol types, and screenshots of the blocks used to make the symbols.
I hope you find it useful!
