Which is the right version to use (0.0.0.0 or 1.0.0.0) for Factory Default Widget Providers?

I would trust the more recent information (the article). From my understanding, setting the version to 0.0.0.0 is recommended while developing the provider, and then setting to 1.0.0.0 and upward when releasing and updating.

Thanks, Steven.  I'm finally starting to wrap my head around all this stuff - where things get written when files get modified in the Widget Studio, etc.

I'm actually in the process of refactoring the code from that Samples repo into a more generic helper class library with an abstract FactoryDefaultProviderBase where inheritors implement the Installable Files property in a partial class that gets modified by a refactored version of the File Manifest Updater project. 

Sounds like a helpful base class. As for the version number in an IInstallablePlugin, all that really matters is that the number is increased from the currently installed version when you intend for its Install() method to be invoked during plugin initialization.