I'm surprised that there is no mention of the recent big improvements in the GIN infrastructure that Postgres full text search uses. The 9.4 release notes list:
* Reduce GIN index size (Alexander Korotkov, Heikki Linnakangas)
* Improve speed of multi-key GIN lookups (Alexander Korotkov, Heikki Linnakangas)
* Reduce GIN index size (Alexander Korotkov, Heikki Linnakangas)
* Improve speed of multi-key GIN lookups (Alexander Korotkov, Heikki Linnakangas)