The problem with tree-shaking is that it's recursive -- every module has to do it properly, and at the moment, I'd wager most frontend modules in NPM don't.

If I responsibly say `import { map } from 'lodash'`;, but (say) my frontend rendering library says `import _ from 'lodash'; _.map(things, func);`, then unfortunately, transitively, I'll still get all of lodash.

Strange, I have it working with rc3. I have an ES6 module exporting tons of Array utils. I definitely see the build size fluctuate depending on whether I import 1, 2, etc of these util functions, whether with webpack 1 (or most bundling tool apart from rollup) I would pay the entire file's price upfront.