Regarding JSON, I would suggest adding XML alongside HSTORE as related
features which allow a No-SQL-like approach. JSON and XML can be thought
of as equivalent formats (alongside HSTORE) and while there are perhaps
different features there, it helps emphasize the flexibility that
PostgreSQL has in these areas.
You are already positioning JSON as one feature among many related ones,
and adding mention that we already have XML support just bolsters the view
that we are committed to these workflows.
Hope this helps,
Chris Travers