I made a little comparison: I drove a little trip by car and recorded it with Maemo Mapper on N800 with LD-3W GPS unit and with ecoach on N900 with the internal GPS. The GPS update interval was 5 seconds in ecoach while Maemo Mapper updates every second. The distance calculated from the gpx recorded with N800 was 27.1 km and from the N900 recorded 26.9 km. I forgot to take a note what was the distance measured by my car. I have previously compared the N800 recorded distance to the distance recorded by my car and it was within 1%.