Last weekend the Secret Diary of Steve Jobs proposed a way for disgruntle iPhone users on the AT&T network in the USA to protest against the behaviour of AT&T. This also sparked the creation of a Facebook Fan page.
3G GSM networks requires a dense cell configuration and AT&T may not have enough cell towers to cover the vast areas that their network serves. On the other hand, playing the devil’s advocate, AT&T’s 3G network, like the ones in Australia, is still immature compared to other 3G networks around the world, so the US population needs to give the company time to build up the network to a more mature level.
All the user complaints about the iPhone in the US and Australia are not specific to the iPhone, but the iPhone just exposes these deficiencies in the respective networks due the ease of use of its data capable applications.