Right now the only field returned is session_id but http://docs.couchdb.org/en/latest/api/server/common.html#replicate defines multiple fields that are to be returned.
The reason I care is that I am trying to use Ektorp who is following the spec so fields like 'ok' (which arguably shouldn't be there, btw, this should be handled by the HTTP status) aren't properly set causing code to think that a replication failed where it actually succeeded.