This release includes two major additions.
Epic is an entity above Feature. Quite often you want to have one more level of hierarchy for requirements, and Epic can be handy. For example, you have large module and several features inside this module. Or you have large feature and break it down to smaller, like Minimal Viable Feature and Minimal Marketable Feature.
Follow entities and receive email notifications about changes. For example, you may follow a Feature and receive notifications about its effort changes, new comments, new attachments, added/removed User Stories or their states changes, etc.