I think there are two separate issues with the use of ipad in cockpits - firstly, as an electronic chart display and secondly, use of the ipad's GPS function to provide a moving map type display.
As danglybits suggested, I don't know that there is a restriction on how the chart/DAP information is displayed, so long as it is current. You could have it printed on a roll of toilet paper in braille, and even have a second roll handy for redundancy, I suppose. So I assume same goes for having the charts on ipad. Yes, have a second ipad or iphone or even paper charts handy for redundancy, but even then - has anyone thought of a backup for paper charts in the (albeit unlikely) that the door opens inflight and your maps get sucked out? Perhaps the CASA solution would be to carry a set of DAP/Jepps for every emergency exit on your aircraft, an ipad and iphone, a tablet PC and spare batteries to equal twice your fuel endurance and a new CAO for fatigue and duty limits on electronic devices.
The second issue is probably the more contentious one - use of the moving map function, and I think we all agree - its great for situational awareness but not for primary/sole use navigation!