You guys have access to an Australian dollar auction house and a US dollar auction house. It will be up to you which you prefer to use. The advantages being that there are no currency conversation fees if you use the AUD auction house - on the other hand the USD auction house will have a larger player population.
That allays the last of my concerns on that subject.
Seems strange to me that they released that info by randomly replying to someone in the forum rather than as part of a general News release with all the final RMAH details. But then again it's Blizzard and they leak out useful bits of info quietly sometimes for whatever reason.