I have only recently started to work with ReactJS and have come to really enjoy it. ES6 & JSX are wonderful to write in and React's Component level abstraction is refreshing.
More than that, server generated markup with all content preloaded is exactly what I've been looking for in a modern UI framework. You still get all the CSS/JS animations baked in on the client and your markup is not littered with bizzare attributes. This site is written with React and serves as an example:
If you cURLed this URL, you'd see the generated markup does not differ from what is in the browser.