Xamarin as a platform has made great advancements in the latest 1.5 years. I have been using it for 2.5 years. Haven't had a chance to play with React yet, which HN seems to leans towards. When I stared my app building platform startup, I had to pick between React and Xamarin. Ultimately picked Xamarin because we already knew the platform and Forms was mature enough, whereas React wasn't that mature imo (few apps outside the facebook dev team were big in scale). Xamarin Forms has its issues but now that it is open source the community can tackle those issues together. Happy with my choice so far, Xamarin has a great community.