[Update! Google has just added Australian road information to Google Earth!]
Sweet, Google has just announced extended support for the Google Maps Australia site. You can now perform business searches and get driving directions.
Now, if they could just add the Google Maps road information to Google Earth…
[BTW, until they do, you can use this tip as a workaround; it will download the correct ’tile’ from Google Maps and semi-transparently overlay it in Google Earth.]