I didn't think JSX made sense until I used it in Typescript (TSX). Having type safety and refactoring support in views and templates is wonderful. I know that both Vue and Angular have worked to build Typescript compiler plugins to support type checking their view files, but TSX is out of the box, has great editor support, and gives you the full power of Typescript's downleveling transpiler, too.

For what it is worth, the project I'm primarily using TSX in isn't using React either. It's built with Cycle.JS which uses competitor virtual DOM Snabbdom.