> MCollective (which Puppet Labs acquired several years ago) was (and remains!) fiendishly complex to set up. I didn't find MCollective hard at all - you just install some debs, a message queue server (Stomp was easiest at the time - it's now deprecated, but surely is not much different to RabbitMQ?) and it Just Worked for me. And there was a great screencast. Did it get far more complicated since I used it last?
RabbitMQ works but is slightly problematic since the authors have a morbid penchant for not wanting to support anything but Apache ActiveMQ. Ask a question about MCollective and RabbitMQ and the answer you get is 'switch to ActiveMQ'.