You can export a route from GMaps as KML by copying the link for the map and pasting it into a browser's URL bar with "&output=kml" appended to it. GEarth, of course, knows how to open KML files.

Google moved some of the options that used to be in the upper-right of the map to the space above the route directions (i.e., the part that's not visible if you've expanded the map to fill the width of the browser window).