How people are using this

Atila uses it to load test his various versions of MQTT:

• https://atilanevesoncode.wordpress.com/2013/12/05/go-vs-d-vs-erlang-vs-c-in-real-life-mqtt-broker-implementation-shootout/
• https://atilanevesoncode.wordpress.com/2015/11/09/rust-impressions-from-a-cd-programmer-part-1/

NinjaSphere uses it in their product, though the company seems to be on hold, or only mostly dead:

• https://github.com/ninjasphere/mqtt is forked from jeffallen/mqtt and is used in https://github.com/ninjasphere/go-ninja/blob/master/bus/TinyBus.go