My opinion on this matter is that GPSDrive is sufficient for desktop use. I never intended to try to replace GPSDrive in any capacity other than on the Nokia 770. In fact, Maemo Mapper's code is highly optimized for the Nokia 770 and its screen, so major code changes would be required to get it to run on a machine with a higher resolution.

The only downside to GPSDrive is that (I think) it uses 1280x1024-sized tiles, and the filenames are in a particular format (different from Maemo Mapper's), so it can't use the same map cache as Maemo Mapper (which uses 256x256 tiles). I don't see this as a huge issue, though, since the Nokia 770 and a laptop have vastly different storage capacities, so you would probably want to have different caches anyway.

It's certainly possible to port Maemo Mapper to the desktop, but I would probably never consider integrating it into the current codeline, instead forking it into a separate project, at which point it starts turning into GPSDrive. It would probably be easier to just patch GPSDrive to work with Maemo Mapper's tiles.