Typically, you'll get a very quick - within about five seconds in our experience - lock on your relative position, followed by absolute GPS positioning within a minute or so. The inbuilt Maps application uses Google Maps to provide either a flat 2D road layout, Google Earth's satellite view, or a hybrid of the two approaches. There are no spoken directions, but it is possible to plan trips. We'd advise having an incar navigator to read them to the driver, however, as the lack of a 3D view makes reading the GPS screen a touch tricky.
Where it gets more complex for Aussie users depends on your carrier and network quality, as all the maps have to be downloaded dynamically. Within a good 3G coverage area this isn't much of a problem, but if you do get into a bad signal area, or have to drop to 2G data, Google Maps struggles to keep up. In the interests of technical accuracy, we took an iPhone 3G connected to Optus' network for a drive up the F3 freeway outside Sydney, and can report that the data speed of the network is around 65Kph - as in, that's the fastest you can drive in a 2G area and still have Google Maps keep up reliably.
Where the GPS remains in flux is that the current Apple software developer's kit prohibits the development of 'Real Time Route Guidance' software - that's the kind of thing you'd find in the average Navman GPS, for the layman. That's Apple's current position, and we can only hope they reverse it; the iPhone's large screen and, say, TomTom's approach to simple GPS guidance (along with already downloaded maps) would make the iPhone truly excellent. As it is, the GPS is merely adequate, and that's a pity given the potential.
