Lots of people use React as the V in MVC. Since React makes no assumptions about the rest of your technology stack, it's easy to try it out on a small feature in an existing project.
React is an open source tool with 130K Github Stars and 23.8K Github Forks. Here’s a link to React's open source repository on Github
Here are some stack decisions and reviews by companies and developers who chose React in their tech stack.
3123 companies use React including Airbnb, Facebook, and Uber.
Redux.js, Firebase, Sentry, Meteor, and Algolia are some of the popular tools that integrate with React. Here's a list of all 127 tools that integrate with React.