The best part about OpenStreetMap (OSM) is that it's like a wiki for maps. If you find some place where you get misrouted (e.g. wrong way down a one-way street), you can just pop up an OSM editor, and fix it. As soon as you hit 'save', your changes are in the map and shared with everyone.
The reverse side of that coin is: if OSM makes you happy, plan to re-create your mapset once a month, because the map is growing that quickly.
If anybody is curious about editing OpenStreetMap, drop me an email: russ@cloudmade.com