Aussie Bob:
IMHO for private operations just an Ipad will suffice. The backup is up to the pilot, not casa.
Correct, but you do need a backup in some form. Personally, I keep the paper charts. I also find when touring, that marking our position on a paper chart is something useful a passenger can do to keep them occupied as well as satisfying the VFR position determination requirement.
The latest definitive guide for AOC holders covers the issues I think.
http://www.casa.gov.au/wcmswr/_asset.../ops/233_1.pdf