- Styles colocated with markup/logic (I consider this an advantage with a component library like React, others may not)

- No global styles stomping on each other, styles scoped to a single module unless explicitly exported/imported

- Type safety, if using TypeScript

The main downside is often performance, though

We're solving the performance pitfall of CSS-in-JS libraries by making a compiler instead. In the vast majority of cases, there should be zero runtime cost to using StyleX.

Refactoring and knowing where styles are used. In css sometimes the btn class does something and sometimes not. With stylex it is explicit.

Styling based on js, eg striking through if an item becomes deleted, etc