One thing that is important for routing is that roads don't simple cross each other but they are connected. In the past few weeks I also came across a few roads where people tried to trace numerous roads in the satellite pics in a single continuous line that crossed and overlapped itself. There is a web service called Map Roulette that tries to detect connectivity errors and randomly presents them to users of the site for correction. So things should get better over time if you periodically download new maps.