With the recently added NPM support added in 3.1.0alpha3.4 and some popular React ES6/Typescript starter kits being deprecated in favour of CRA (https://github.com/facebookincubator/create-react-app), I wanted to finally try out importing GUI with CRA + TypeScript. Thought I would put up a repo for anybody interested.
Here is the demo: https://brianzinn.github.io/create-react-app-typescript-babylonjs/
Source: https://brianzinn.github.io/create-react-app-typescript-babylonjs/
Source for page with BabylonJS: https://github.com/brianzinn/create-react-app-typescript-babylonjs/blob/master/babylonjs-site/src/containers/home/index.tsx
So, it's pretty straightforward from the docs (http://doc.babylonjs.com/overviews/npm_support), but also in practice turned out quite fast to get started.