The three gsm carriers have reasonable coverage. They are Telstra, Optus
and Vodafone (all other retail offerings use one of these 3 carriers). I
use Vodafone - simply because their rates are best for my usage pattern.

I have to disagree here. Our experience in going to rural Queensland is that
our Optus & Vodaphone GSMs often didn't have coverage even in reasonalble
large towns, and the locals were all using Telstra. But yes Telstra tends to
be more expensive -- you get what you pay for, I guess. If you want to
maximise coverage, it's got to be Telstra.

Kerry