We have released Social Stream 0.5. In this version, we have splited the basic functionality in social_stream-base gem. It provides two types of actors: users and groups, and two basic types of activity objects: posts and comments.
In the next months, we are developing more modules for Social Stream: attachments, images, videos, events, and even social network federation! The social-stream gem will provide a social network platform with all the bells and whistles. However, we want developers being able to customize their social network application using only the modules they consider the most appropiate. Of course we are open to contributions, also related to new modules!
This version is pretty stable. However, we can not assure a consistent stability until Rails 3.1. The latest version of Rails comes with a bunch of functionalities pretty convenient for engines, The new asset pipeline simplifies our asset management considerabily, including better support for themes. jQuery is now the default, this will clean up some stuff. Besides, the engine migrations enables a flexible management of the database scheme. Rails 3.1 is in its release candidate 1, so the stable release should not take long. Stay tunned!