We used Angular at Stampsy and it was a pain to learn and debug. React is awesome because it encourages very modular components, has very small API surface (you can go far with knowing 5 API methods, compare this to Angular insanity) and great out-of-the-box performance (which is possible to boost 5x if you use performance hooks like `shouldComponentUpdate`). React gets you very close to browser limits in terms of perf, while staying very maintainable. Moreover, it doesn't impose any kind of structure on your projects, and you can begin using it one component at a time (even inside Angular).

(I'm not affiliated, just a very happy user.)