I am rather comfortable writing concrete schemas with explicit primary keys, foreign keys, indexes, views and stored procedures. For queuing I use a NoSQL solution called: Redis.
This significantly minimises data conversion; as JSON is used natively across the board.
Are the performance gains from data consistency enough of a reason to develop in NoSQL, rather than relational?
PS: Should note that MongoDB uses BSON, so that could be interchanges for something like CouchDB (correct me if I'm wrong, but that stores as plain JSON)