JavaScript Modules
The problem with introducing new keywords and doing this in a backwards incompatible way, is that we'll be running with three module systems for years: CommonJS, AMD, and ES6. As far as I can tell, and please correct me if I'm wrong, it looks like ES6 modules aren't solving any new problem that CommonJS did not solve. Browserify does an excellent job of bringing CommonJS to the browser and it's gaining a lot of momentum. With ES6 now pushed back until June 2015... I'm not sure what to think anymore.