Ask HN: Best Practices for CSS in a Modern JavaScript App

So I feel I have a pretty good idea of the tools and techniques available for modern javascript development (React / Angular / Webpack / Typescript / Redux / Mobx / Electron etc..), but when it comes to CSS I am pretty much lost, there seem like a ton of options (postcss / sass / less / css modules / radium / react-css / cssnext etc.) and I don't really have an idea about the various trade offs involved.

I would be very interested to hear:

- What are you using?

- Why did you choose this?

- What do you like?

- What don't you like?