As if the churn wasn't already bad enough, I've recently started using JSPM[1] and it's pretty awesome. I'm writing ES6+ code with hot reloading react components.
If you're trying to decide between build systems I would recommend checking it out, and watching this video[2] for a nice overview.
[1] http://jspm.io [2] https://www.youtube.com/watch?v=iukBMY4apvI