Despite Maps originating in Google's Australian office, we've got this option long after the US and other countries. You can search using general terms as well as specific addresses, and use voice search rather than typing. Walkers can even set a special mode where the phone vibrates to tell you when you need to make a turn.
While having one less device to carry is appealing, bear in mind that using a mobile phone as your GPS will chew through your data allowance. The amounts involved aren't necessarily huge, but it's a risky option if you don't have some sort of data plan in place and are paying OTT casual rates.
Thanks to all the readers who wrote in to point this out and especially to Adam for the screen grabs.
Google Maps Navigation comes to Australia [Google Australia Blog]