ClojureScript๏ Namespaces without the tedium๏ Can modify native prototypes freely (because of ubiquitous namespacing). Want to add methods to NodeList? Go ahead!๏ Ships with rich abstractions - invent new APIs only as a last resort. Bye, bye interoperability nightmares.
Browser REPL & Friends๏ Develop against any browser live without refreshing๏ Richer data structures - Sets anyone? ๏ Rhino works, Node.js another great target
The Compiler & Friends๏ ~1000 lines of code๏ Easy to hack๏ Google Closure Compiler works incredible magic - inlining, renaming, dead code elimination
Language Features๏ Add language features via macros๏ Hate callbacks? Add delimited continuations๏ Want Scala/Haskell style pattern matching - it s a library
Clojure(Script)๏ Robust proven backend technology๏ Can now leverage the same powerful abstractions on the client๏ The language can be incrementally grown (via libraries) to adapt to the unique and changing needs of your project