if it's about simplicity, then Javascript and Node are better at concurrency for me when it comes to I/O, Node is very performant too
I keep expecting someone to write one and put it up on NPM (I haven't looked recently, though). Perhaps I should clean up my and stick it up there. It provides a very nice abstraction of continuations. I did it merely as kata to show that continuations do not require concurrency.
https://github.com/olahol/node-csp