I partly agree with FDTK & C Claret. Telstra is a nightmare and if there was any option at all I'd change. But NextG is the best game in town. I had a small fleet of CDMA phones with guys working (in cars) in NW Vic / W NSW & Nth SA. It took us ages to get Next G to an equivalent level of reception. Its very dependent on handsets. Anything without the Telstra blue tick is only useful as a paperweight. We now use the LG flip phones and with external aerials we get better reception that we ever got with CDMA. I have both one of these phones and an iphone and frankly find that the iphone is close enough to the same coverage as the LG phone that I don't bother with the LG phone anymore. The iphone's big screen can be useful for weather radar in flight. I seem to have more coverage problems over suburban areas (I was once told that Telstra can make the base stations vertically directional) but have few areas of non coverage once I'm going. I'd do the iphone. But you do need to be organised to be able to charge it each and every night and occasionally I need a top up during the day.
Did I mention that I hate Telstra?
BTW, you need to check the Telstra bills carefully. They are frequently wrong. Last year most months I had a $1000 credit each month for errors. I find that Telstra's bills are basically wrong the first month you add or delete a number or make any other changes.
PS the AWIS app for the iphone is really good.