The only problem booking through expedia is when changes occur. Over ½ my bookings have had flight/time changes and it's a relatively simple process when booked on aa.com to call the AAustralian AA number to get it sorted. (I do tend to book well in advance).

Expedia, well, that's another issue ...

Also, there is the Aussie AA web site option: http://www.aa.com/content/au/index.jhtml