We use if for migrating test/development Joomla sites to live sites. Or domain X.com to domain Y.com scenarios.
It handles all the permission and domain issues without any problems.
This is as great a tool for migrating sites to new domains as it is for backups IMO. No more hiding development sites until ready get the basics up and carry on working on the development site and then migrate it over again when ready or updated.
Brilliant - well done to the developers.