github-backup is repository-focused. It does not try to back up other information from GitHub. In particular, social network stuff, like users who are following you, is not backed up.
github-backup does not log into GitHub, so it cannot backup private repositories.
Notes added to commits and lines of code don't get backed up yet. There is only recently API support for this.
The labels that can be added to issues and milestones are not backed up. Neither are the hooks. They could be, but don't seem important enough for the extra work involved. Yell if you need them.
So, it backs up most of everything, just a couple of the deeply commented stuff doesn't work. All issues for example get backed up. It feels more like it back "most" things up and leaves out only a couple of things.
