I recently put a lot of effort into working with the relatively new messaging queue protocol, AMQP. This involved reading the v. 0.8 spec., source code of some implementations, the RabbitMQ docs and boards, and the source code of the py-amqplib module.
Ultimately, I could not get the AMQP client and broker to behave in ways that I expected. This is a real disappointment because I had high hopes for it in future projects that will need to be scalable. I'll give it another 6 months to a year and then see where things are.