We are pushing an update to the osgEarth::Config API.
This should affect very few. Using the Config API directly is not necessary (and highly discouraged) unless you are into advanced stuff like making your own custom Layers or TileSource drivers.
For those that do use it, we consolidated all the various getter/setter methods into just three: set, get, and add. We also added a macro called OSGEARTH_SPECIALIZE_CONFIG so you can support your own classes in the Config framework just by adding a getConfig methods and a constructor that takes a const Config&.