It looks like in 9.4 PG went after the document databases and now they are after Oracle. I don't know why I get excited with point releases of postgres, but I do.
Its not just that. I waited patiently for 9.4 to come out as I needed just that functionality of indexable JSONB for something I'm working on. It was pointless for me to start the project without it. 9.4 came out better than I could have expected. Then followed by Upserts, and now this... I'm directly and personally affected by each point release. Its fantastic.
"mySql" is dead to me. Literally. Anything Oracle touches becomes a potential legal liability. Its Maria DB now and although I do maintain a legacy 100GB+ MARIA db, I will never use it again for new projects. The thing about postgres is that once you start using it you understand there is really very little competition in both the open or commercial worlds. My previous big project relied on mongoDB for statistical data. At the time there was no other compelling document database for our use case. Today, this decision is no longer relevant because if I can get the same functionality and performance out of Postgres I will choose postgres. The ability to combine the SQL with "NoSQL" is just too compelling.