Telstra has (by far) the biggest coverage in Australia - 96% of population. Even though Optus and Vodafone might be within a % or 2 in population coverage, the population density in some areas of Australia is very low.

Most Telstra base stations are 900/1800 GSM compatible.

Telstra also has a network here with better coverage than GSM, being CDMA (800 MHz). If you have a US CDMA 'phone, it might be worth checking if your provider has roaming with Telstra.

More info here: http://www.telstra.com.au/mobile/net...erage/maps.cfm