Solution: TrailRunner supports the following OSM Render Styles: Classic OpenStreetMap, OpenCycleMap and CloudMade Fine line. To switch between these, Goto to Bottom Toolbar > Background Map > Display Settings. In the left pane select any of the available OSM tile servers.
Tip: As tiles are heavily cached in TrailRunner, you may want to right click the map and reload background maps whenever you see outdated tiles being displayed from the cache. To reload all osm map tiles, delete the following folder: < yourhome >/Library/Caches/TrailRunner/MapViewTiles/openstreetmap.org
Reason: TrailRunner loads maps from internet services that provide free maps. If the loading process is slow, the map service is slow and TrailRunner can't get anything faster. Another reason are "fair use" agreements for commercial web services. This means that as long as you get maps in a fair amount and frequency, the commercial service won't put you on a black-list. For that reason TrailRunner throttles the keyhole imagery service.
Solution: TrailRunner caches maps. If you have once loaded map fragments from a service, it's unlikely you will need to load the same fragments again. The longer you use TrailRunner, the faster it will become.
Tip: In case the map material on the web service was updated, as it is frequently the case with openstreetmap.org, you can use the File > Consolidate > Reload background maps command to reload what’s currently visible or you can remove the MapViewTiles folder in your Application Support/TrailRunner folder.