[yodsanklai]

CSP ideas have been used in Erlang, Scala (and you say Clojure). But CSP is earlier the pi-calculus. So that's not a good argument for the value of the pi-calculus.

Compared to CCS and CSP, the pi-calculus allows for natural transmission of communication links (think object references in java RMI for instance), and it uses an elegant formalism to do so (scope extrusion). At least, I would say that pi-calculus ideas are useful to give a formal semantics to certains concurrent or distributed languages, which in turns open the door to program verification.

It has also been used for protocol verification.

[juliangamble]

Thanks - that's a helpful clarification. I agree there isn't a direct link - it's more like you have to "widen the lense" within a field of related ideas to get from pi-calculus to CSP.