
Google released v3.2.1 of Google Maps for Android on November 24th. It's for the US only. This version includes turn-by-turn audio and visual GPS navigation.
But within a few days, there were alternative android ROMs available that included a version of Google Maps with support for Navigation outside the US. I've tried it here in Auckland and it was perfect all the way from the North Shore to Titirangi and back. You want this.

So if you want to get over to the market and try this out, here is the QR code. Scan it off the screen with your phone and it will take you to the market and direct to the app. You'll need to have "Barcode Scanner" installed.....but surely everyone already has that installed? If not, get it. It's very useful.
Now I just need a little stand on the dash of my car to rest my phone in when I'm driving so I can hear the instructions, though I think the Bluetooth 2.0 A2DP stereo support in my HTC Magic may come in handy if I wear a headset.