Nick Salem of Neustar recently shared some impressive performance gains realized using Oracle Spatial 12c Vector Performance Acceleration, in a Google+ post. He observed performance gains of 40X to 300X -- with a use case aggregating all ZIP Code geographies in California using a SDO_AGGR_UNION operations (plain and with group by/mod functions as described in 11g documented best practices).
Read more details of his test case and results here. https://plus.google.com/114373574274269737617/posts/2caAypKxwff
Thanks for sharing, Nick!