As a long time Common Lisper, allow me to disagree. The STM and concurrency features of Clojure are what brought me in, and they certainly haven&#x27;t been &quot;done before&quot;. Common Lisp&#x27;s concurrency story was always poor.<p>You could also argue that the effects of lazy evalutation and transducers could have been achieved before using SERIES package, but then you surely haven&#x27;t tried to actually use and debug SERIES code.