[zbentley]

Database-as-queue tends to run into performance ceilings before dedicated "true queue" systems, in my experience. As you point out, though, sticking with an RDBMS gives you nice transactionality. Additionally, using a database for a queue for as long as you can before switching also offers you the benefits of using a time-tested, usually widely-supported protocol with well documented reliability guarantees. Your queues are also easily introspectable, which can be nice (this is part and parcel with why databases tend to hit perf ceilings as queues though).

RabbitMQ also supports transactions for some queue operations, but its notion of "transaction" and what you can do inside of one is much more limited than a typical database's: https://www.rabbitmq.com/semantics.html