When TomTom for iPhone in Australia appeared in the store this morning I didn't hesitate to purchase it, even for AU$99. The download is 157.1Mb, which seems modest given that the maps are built in. I'll give my existing hard TomTom to my wife so it's not really a duplication.
Choosing a destination involves choosing the major city, like Sydney, and then searching for the street which is an improvement. The map is no-where near as nicely designed as Google maps.
When you pan the map it erases and completely re-draws, which is a step backwards from the browser based Google Map. I'm assuming at this point that the routing algorithm is the same as their other devices so probably pretty good but we're hitting the road shortly and I'll report back soon.
Obviously I'm now in the market for a car mount with charger.
The Australian "Ken" voice sounds loud and clear through the iPhone speaker. The interface is familiar to users of the normal TomTom devices. Route re-calculation is really fast.
When you turn the phone on its side, the screen re-orients to that format as you'd expect.
The biggest disappointment is that there are no computer synthesised voices so there is no pronunciation of street names. This is a significant disadvantage compared to the "hard" units and I hope it will be fixed in a software update.
During operation the screen stays lit and the iPhone feels warm so my guess is that a car power source will be needed for full time use. Position updates are very frequent and I feel that the GPS hardware in the iPhone is possibly better than in a hard unit.