MMapper is near perfect as is. This being said, if I were to think of improvements they would include the following….

Specific Data Info Area -- similar to the existing GPS Info Panel create additional panels (same location, size, and form factor as GPS panel) for the following;
GPS Info Panel – as is
POI Info Panel – POI listings of POI’s that are on map the closest on top
Route Info Panel – Data for directions, turn by turns, with the next turn at the top so that as you drive it cycles thru the route. This would help due to N800’s volume issues, and the fact that the radio is always on.
Map Info Panel – zoom levels available for that location, size quantity, layer info
These could be visible one at a time in the same space as the existing GPS info, and prevent the need to access menus, something difficult to do when driving.

Layers – Allow transparent maps in overlays or layers. For example MS MapCruncher has tools to extract particular colors form a scanned map say the blue of a bus line and then use this mapped transparency to overlay as a layer the base map. This could be used for traffic info, bus routes, hiking trails.

It would be great to have a visual indicator of which maps are available at other zoom levels for that GPS location. This could be displayed as part of a Map Info Panel mentioned above.

If a Companion App is done for non – Maemo environments, it would be great if both could share the same db format and act as a method of loading maps, layers, POI information and creation, and trip planner (route generator) for example.

Hope I did not duplicate items in the forum already. MMapper is a great app and I look forward to seeing what is done for v2.