One big advantage of using Google Apps is that you can take advantage of Gmail and Google Drive while keeping your own company domain for email. Google has expanded the range of domains it offers for new sign-ups to include 22 new country-specific options. Unfortunately, Australia isn't on the list.
If you already own a relevant local domain name, you can use it with Google Apps, but that requires a little configuration. If you're setting up a new business, being able to acquire and configure the domain as part of the Apps signup process can be handy. Google is now supporting the following domains for registration on sign-up, including 13 country-code specific options:
We've asked Google locally for comment on why '.com.au' isn't included in this list, and will update if we hear anything. It seems likely that the higher prices and stricter rules associated with Australian domains might not have merged easily into Google's system. Australia isn't the only exception; there's nothing for the UK or France either, for instance.
Google Apps domain registration has gone global [Official Google Enterprise Blog]