The only thing you should do is migrate the database schema to ensure RailsCollab's models continue to function. This can be achieved by running the following command:
rake db:migrate
If you are updating from the rails2 version of RailsCollab, the default location for Company logos, User avatars, and File data has changed. These are now located in "public/system/logos", "public/system/avatars" and "public/system/data". If you have any existing files you should be able to copy them to the new location to make them work again.
Thats it!