Among other things, I learned that:

      the powerful type system eliminates a large class of bugs the compiler eliminates the long name spaces (and the corresponding run-time look ups)
      getters/setters actually lead to better compression
      you can split the client side code in multiple, independently loaded modules
      the pseudoclassical pattern used for OOP is actually better than the functional pattern (when combined with the Closure compiler)
      you can easily extend the Compiler with extra features...

These sound very interesting - it'd be good to have an explanation of these points.