I've been using it in production for a number of applications for about 6 months now and haven't seen any performance issues. Prismatic http://getprismatic.com/

I've been using it in production for a number of applications for about 6 months now and haven't seen any performance issues. Prismatic http://getprismatic.com/ http://getprismatic.com/ and CircleCI https://circleci.com/ https://circleci.com/ both use ClojureScript for their front-ends. CircleCI open sourced their front-end here https://github.com/circleci/frontend/tree/master/src-cljs/frontend https://github.com/circleci/frontend/tree/master/src-cljs/fr... as you can see it's a decent size app, and Prismatic have blogged about Om and performance here http://blog.getprismatic.com/om-sweet-om-high-functional-frontend-engineering-with-clojurescript-and-react/ http://blog.getprismatic.com/om-sweet-om-high-functional-fro... In general, there should be very little overhead compared to regular JavaScript once the advanced compilation option is used.