I built our entire monitoring infrastructure on top of nanomsg and nodejs; previously I used zmq. Over the last 3 months, I've had absolutely no issues with a bit over 200 servers communicating with each other.
I used nanomsg to have 20+ servers listening to queue from a single master.
I found that over time the memory consumption would rise horridly and I had to stop using it. I've just had another sanity-check of my code and don't spot an obvious leak, but I'm willing to believe it is there:
Pretty cool stuff.