Ranked in these QuestionsQuestion Ranking
Pro Allows you to develop native apps
Pro Backed by Facebook
Facebook writes their mobile apps in React Native so the code base gets pretty thoroughly used in some highly demanding scenarios.
Pro More predictable control of the state
The one way data flow, makes it more predictable and easy to control.
Pro Provides a native experience
Through using Titanium's API and UI components similar to that of the platform's native UI, Titanium provides a native experience.
Con Steep learning curve
Con If core team doesn't use a certain feature, it's not developed
Whenever there's functionality you need that they don't use in their apps, it's not going to get developed by them, even if it's obvious it should be in the core. They always say to either submit a PR or create a separate module.
Con Has specific requirements with regards to installed libraries
Prices start at $39/month for an indie subscription. For a team account, the price is $249/month per seat.
Con Most plugins are paid
Appcelerator Marketplace is meant to sell to developers 3rd party plugins and functionalities as well as code samples. Thus, people will prefer to sell you their plugins and samples instead of making them open source. This will increase costs of development.
Con Lack of capabilities
For example, there is no way to read QR codes natively.