I don't know how I could do without it.
Once has been a great tool for system repair. You could solve every problem with this. After the project has absent-mindedly dropped Truecrypt totally, suggesting migration (how, without the tool?), I can no longer recommend it. The project chiefs don't answer requests, obviously don't care. Furthermore, the disk is still missing any documentation while being booted. Either you know what you can do, or you can't do it.
Very difficult to install