This release introduces storage changes to support revisionable translation metadata, that was introduced in #1046282: Make the module work with revisions. This feature is disabled by default on existing sites to avoid problems with the upgrade path, instead it is natively available on new installations. People upgrading from earlier versions are strongly encouraged to backup their site database before proceeding.
This release includes a huge number of new features and requires core at least 7.15. Many parts of the module changed since alpha2, hence you should backup your site and test it carefully when upgrading to ensure everything is still working for you.