I’ve updated the original post to match Ionic 2 Projects: updating to beta.6.
angular2-polyfills contains reflect-metadata and zone.js, meaning you need to load es6-shim before you load angular2-polyfills, otherwise change detection for Promises will break. Things can also get messed up if Zone is loaded twice, so if you do add angular2-polyfills make sure to remove reflect-metadata and zone.js from your entries in your webpack config.