I briefly worked for a place that had been through cstore and greenplum before buying into Vertica, right before I started. They were simply hungry for analytical performance and had the cash. It was a really great buy for them in performance but also ease of use.
Hindsight: I was skeptical that they'd left all the metadata (configuration/application domain data) in PostgreSQL while moving the (100x larger) business data to Vertica. At this point I'd repeat the pattern just for the sheer delight of dealing with a complex application schema in PostgreSQL. The flexibility demanded of Vertica was decidedly less in that shop.
This deserves a closer look. It appears to be making use of the ORC format used in Hive, and last I looked was implemented in Java and tied in tight with the Hive arch. So this must be a rewrite of an ORC reader/writer. Selfishly I wish they'd picked Parquet instead of ORC.
[0]: http://www.pgcon.org/2014/schedule/events/643.en.html
[1]: http://www.garret.ru/imcs/user_guide.html