I've been working with JSS for my new job.
While it is great to be branching out into javascript based styles, I feel like this works a bit against me. I'm definitely stuck in a habit of using SASS for everything or just raw CSS, but it's so frustrating having to camelCase my style properties.
It's good that you can pass variables through, but I feel like the idea just isn't all there. There are a lot of options around and as this article aptly explains there's a lot of fragmentation.
I'm going to have to get used to it because it's everywhere and that's the direction Javascript (and my job) is taking me. There are good things, like avoiding the constant class name clashes that come with SASS or raw CSS.
Actually, that might be the only good thing, that and the styles are closer to the components you are working with (in React), but I wonder if there's another, possibly better way to do this.