This likely has been in place for a while, but reader Robert points out that Apple's free bumper program for users fearing iPhone 4 reception problems is now officially on the Apple Australia web site. Customers who have purchased an iPhone 4 can apply for a free bumper via a downloaded application, which they need to do by September 30.
The general consensus seems to have been that iPhone 4 reception issues haven't been a major issue for Australian buyers, given that unlike the US the load of new users is spread across several networks. The fact that Apple's reception-measuring patch was in place prior to launch may have also helped; hence, we haven't revisited the topic since iPhone 4 launch day. Even so, if you have bought an iPhone 4, it's worth getting the free bumper to help minimise any potential antenna issues. Thanks Robert!