My favorite part was that I could use React to create both web, desktop applications as well as mobile apps without having to learn 2 different frameworks - it made my life easier! It's not so easy for beginners like myself. There are some features which can be better explained or more intuitively designed by making use of examples. The best thing about this framework is its flexibility in building all sorts of Apps (both Web & Mobile). Also great support from the team behind preact.js. We have used react js across multiple projects but we always ran into issues when integrating new libraries into our existing code base. This has been solved very easily since we started using preact.js.