An R18+ rating is fantastic thing. Pretty much everything that was RCed should be able to be reclassified as R18+ now.
Very few games have been banned/censored in Australia. People exaggerate how bad the classification system is. Duke Nukem Forever featuring poop throwing, crazy gibbing/dismemberment, strippers and a shit ton of swearing was released uncensored as MA15+, people saying 'All games are censored in Australia' are taking it WAY out of proportion. It's not the bad.
They can still technically enforce censorship sadly... another obstacle for another day. But like I said, its a step in the right direction.
That's true, anything exceeding an R18+ rating will still be RC'd but I doubt anything will unless it's some sort of sick necrophilia simulator or something...
Also, taking what you said, in the USA anything rated AO by the ESRB is basically banned on every platform but PC (basically...Microsoft, Nintendo and Sony don't allow AO rated games on their platforms, almost every retailer including digital distribution refuse to sell AO games) So, it isn't banned but the developer/publisher really has no choice but to edit it to accompany an M rating so it can actually sell. The same thing applies to movies in the USA (watch This Film Is Not Yet Rated)