The CartoDB.js beta release offers several key benefits to developers, including continuous improvement through testing and iteration, unification of mapping libraries for flexibility and ease of use, better support for CartoDB visualizations on websites, and full control over customization options. The library also aims to reduce latency and improve performance with its availability on a content delivery network (CDN), allowing for faster website loading times. Additionally, the release includes features such as versioning, bug reporting, and a user thread for support, making it easier for developers to report issues and request help. Overall, CartoDB.js is designed to provide developers with a powerful, easy-to-use tool for building online geospatial applications.