PostgreSQL JSONB: when does it make sense over a separate NoSQL store?

our current stack uses both postgresql for relational data and mongodb for flexible, document-oriented data. we're exploring if we can consolidate everything into just postgresql using its jsonb capabilities. for some of our use cases, like storing user preferences or dynamic configurations, jsonb seems like a perfect fit, offering schema flexibility within a transactional relational context. the questions are around query performance for complex jsonb structures, storage efficiency compared to a dedicated document store, and the overall developer experience. has anyone moved away from a separate nosql database entirely and successfully used postgresql jsonb for all their document-like data? what were the real-world performance implications and any migration challenges?