The great thing about amAze is that it is written in Java 2 Mobile Edition and therefore works on most modern mobile phones. You don't have to have a phone with an integrated GPS like the N95 to use it. It works brilliantly with a Bluetooth GPS receiver connected to your phone. Two of my friends have installed it on an N70 and N73 and are using it with Bluetooth GPS receivers with excellent results. The amAze site lists phones which have been verified to work with the software and many phones from most major vendors are included.
Even if you don't have a Bluetooth GPS, I'd still say it's worth having as the maps and address search feature are useful even without the turn-by-turn navigation.
The address search is very easy to use and works well:
During navigation you can switch seamlessly between the map view and the arrow view. I have found that the voice prompts are very good and I don't even need to look at the screen.
Here is a Flash video clip from the amAze site which gives an impression of how it works (you need sound to hear the voice prompts).
I was planning to one day purchase a Nokia navigation license for my N95, but now that I have amAze on my phone, I will be able to put the money to better use. It's not quite a Garmin but hey, it's free, and I always have it with me!