I looked at this library in the past and I could not find any usage of it in any open source project. That made me a bit scary, how a library like this with the supposed well thought construction is not used anywhere ?
Few software uses these advanced techniques in general, and it isn't so much about Concurrency Kit. There is a barrier to entry as folks have to invest non-trivial amounts of time in learning more about these techniques.
Some open-source examples: http://www.machinekit.io/ https://labs.omniti.com/labs/reconnoiter https://github.com/Litres/turboxsl Aerospike
I'm sure there are others, if there's anything I'm missing, would love to hear.