Some more info from Google on the Google Maps with Navigation release
Google Maps Navigation is an internet-connected GPS system with voice guidance and automatic rerouting, all running on your mobile phone. Using Google services over your phone’s data connection brings important benefits to GPS navigation users, like using Google search (typed or spoken) to enter your destination; fresh map, business, and traffic data; and satellite and Street View imagery along your route.
This release also includes the new Layers feature, which lets you overlay geographical information on the map. View My Maps, transit lines, Wikipedia articles about places, and more.