User of Couchdb for similar use case...been keeping up to date on a parallel branch of my solution using fireproof instead of couch. Still early, but great potential...stumbled onto fireproof because I was about to write an adapter for couch (well Pouch actually, but same same) to replicate in a similar manner to fireproof.

We are working on transparent replication to Postgres JSON which will make it a lot easier to adopt.