Google can't find much user documentation for XPCOM. Sure, it can find endless references to making new XPCOM components in C++, but that's utterly useless to anyone who needs to know how to use the existing components from JavaScript. This is a huge gap, occasionally touched on by trivial examples of creating an instance and calling a method. Has nobody with a more in-depth knowledge of the componentry written anything about its use? Using components with multiple interfaces? Implementing listeners for handling asynchronous behaviour?
"Rapid Application Development with Mozilla" is no help (great breadth but little depth). Spotty references that exist to the defunct XULPlanet redirect to Mozilla Development Center, but that's pretty useless. Mozilla Development Center articles point back to XULPlanet, which is a joke.
Is this the best an army of open source advocates can muster to promote the extension of The Beast?