"Everyone" is using Babel now. A lot of ES6 features are making their way into browsers and node, but there's so much variation that a transpile step is needed. Babel is nice but currently quite slow. Babel has a REPL you can play with here: http://babeljs.io/repl/#?experimental=true&evaluate=true&loo...
Correct. One of my favourite at the moment is `babel-plugin-rewire`, which is a neat replacement for `rewire` -- allowing easy unit testing in full isolation by hijacking the `import` statements :)
