EDN, in addition to being simpler, also has an optimized transport abstraction, transit, which serializes to application/transit+msgpack (binary) or application/transit+json (often vastly faster deserialization than messagepack because which hits the language native JSON parsers for performance in web browser, python, etc). It surprised me how big a deal hitting native json parsers is, EDN was at the top of our profiler for 100kb payloads but transit+json is zippy. The abstraction also handles value de-duplication and has a human-readable verbose writer.
http://blog.cognitect.com/blog/2014/7/22/transit http://cognitect.github.io/transit-tour/
cool project though, good to see s-expressions become more popular