So you always should be online to use this. In my region / state this is not the case or to expansive in most cases. I'd prefer improving the already implemented cache mode if it is possible: Detect if a tile of a region is outdated in the cache => update. But on the other hand I think this is not possible or the handling to time consuming.
That would mean that POIs that can be overlayed in Google Maps e.g. can be shown in maemo-mapper,too? That would be great if the xml overlay structure (kml?!) by google could be directly imported like a route,track!!