Do you know a way that I can change the application that opens the validation scripts in ArcGIS 10.2? At the moment hitting Edit... opens up Notepad, which ain't that friendly an IDE.
I found the answer to my own question!
For later reference...the default IDE is controlled in the Geoproessessing Options:
Set the IDE by navigating to the exe for your chosen IDE, in my case PyScripter. Hit OK to apply new settings.
So now when I hit Edit... on a toolbox I get this instead :-)