The config keys I've found are pertinent are:
config.assets.enabled = true
and
config.action_controller.asset_host
From what I can tell, the basic functionality is there, although it might require a (either custom or standardized) rake task or the such to accomplish the actual push to your s3 bucket.
One of the issues I've been facing is the when you use the sprockets-based asset pipeline, it likes to add a cache-bursting hash onto the file's name, which isn't included when using the rail's `asset_path` view helper (even the sprocket's version).
Would seem to me that this kind of functionality should be 'end-user/developer' accessible but where to put the functionality: in sprockets or on the rails side?