Are there standards or best practices yet when it comes to multi table inheritance in rails 3? So far the best article I could find was:
http://mediumexposure.com/mu
I recently forked a promising gem to implement multiple table inheritance and class inheritance in Rails. I have spent a few days subjecting it to rapid development, fixes, commenting and documentation and have re-released it as CITIER (Class Inheritance and Table Inheritance Embeddings for Rails).
Consider giving it a look: https://github.com/PeterHamilton/citier
It actually takes some concepts from that article you mention.
For an easy way to do multi-table inheritance take a look at 'acts_as_relation' plugin https://github.com/hzamani/acts_as_relation.
There's a guy in the Melbourne Ruby group I attend that's written a couple of blogs on table inheritance in rails and the comments are really helpful as well. It's not specifically Rails 3 but there's definitely some decent pointers in there.
http://rhnh.net/2010/08/15/class-table-inheritance-and-eager-loading
http://rhnh.net/2010/07/02/3-reasons-why-you-should-not-use-single-table-inheritance
happy reading