With Google Maps 4.2, Google brings turn-by-turn navigation with route planning and voice output to devices with Android 1.6 - until now, users of older Android versions were excluded from the navigation solution, and it was only available in the USA (at least without tricks).
Navigation still requires a permanent Internet connection, so it should not be used abroad unless roaming costs are lower. The only alternative here is to use "real" navigation solutions that store all the map material on the mobile phone.
However, it is worrying that Google is not consistently discontinuing support for Android 1.6, forcing mobile phone manufacturers to develop updates to a newer Android version, e.g. 2.1 or 2.2, and make them available to customers.