Thanks for your kind words, Mark, which I agree with. It really is a remarkable system when you consider the immense complexity it copes with.
The person who deserves most of the credit is the inimitable Eloy Lafuente (stronk7), who is not only an excellent human being, but did the core re-design and most of the coding of Backups in Moodle 2.x over a period of many many months in 2009: http://docs.moodle.org/dev/Backup_2.0_overview
He also wrote the very first version of Backup in Moodle 1.1 in 2003.