Hi I have briefly used Motion X but only as a GPS plotted rather than a navigation tool.
As a plotter of where you have been it is pretty good. If you are using it for something like cycling then you might also want to try MapMyRide as it is free and you can upload the routes you make to their website and share them or export the maps and open them in Google Earth. You can also use the website to create maps that you then load to the phone in order to follow.