The RichFaces project is an advanced UI component framework for easily integrating Ajax capabilities into business applications using JSF.
RichFaces 4 builds upon the pioneering Ajax support that began with RichFaces 3 and is standardized in JSF 2. In addition to extending these ajax capabilities, RichFaces also improves other areas of JSF 2, including usability, performance tuning, dynamic resources, skinning, and component development. This allows users to take full advantage of all the productivity enhancements of JSF 2.
It is my favorite web framework and component library for developing web applications.
It is simple to use the components and to combine them into personalised components.
You are very efficient for building big and very complex web applications.
It as a uge community and the documentation fits perferctly for what I expect for an open source project.
The project has also given an enormous new experience for JSF 2.0 (with ajax and fecelets)
Good alternative to PrimeFaces and can, if you really want to, even be used together with PrimeFaces to create and even larger pallete of components for JSF.
I rather don't like RichFaces. I found PrimeFaces much more fresh and intuitive. A4J seems to duplicatre built-in AJAX capabilities of JSF 2.0. It's of course a stable, production use JSF component set.