Not a direct response, but more a "for what it's worth" kind of thing...

I use Maemo Mapper quite a bit. I've found that:

- the stock version starts to have sluggish panning/redraw issues when the downloaded database gets large (2Gb-ish). Nutter wrote a version ( http://talk.maemo.org/showthread.php?t=16838 ) that saves the maps in files rather than a database format. I use this and I find it doesn't have issues with huge map caches. (edit) The latest MM update might have fixed the sluggish pan issues; I've not tried it.

- it's easy to cache huge numbers of map tiles and I've done this for pretty much anywhere I'm likely to go, in Japan and Canada.

- I never leave MM set to automatically download missing map tiles. I'm too cheap to pay for a data plan and I find the "looking for network" box that comes up rather annoying.

- I've found the VEstreet maps don't complain about bulk downloads and work well for Japan. Generally, I found that when downloading maps, it's best to keep the loads less than 200Mb at a shot, or it tends to start throwing errors. It takes a while (multiple overnight sessions) but when it's done, it's done.

- I only cache odd zoom levels (1,3,5,7, etc..) as when viewing, MM will double-up the lower level zoom on the even levels. This makes the writing actually readable. Yeah, old eyes.

- "Routing" on MM is generally not what anyone who has used a regular GPS would consider routing. Basically, it's a link that gets a website to make a "routing" track. Unless you have some roaming data plan, it's not going to do on-the-fly rerouting.

- the plug-in speech system was useless. When I had it running in the car, the announcer voice was set to something like "English as a second language kidnap victim with socks stuffed in mouth." I shut that off pretty fast. There may be something better now though, I've not looked.

- The track system is quite useful. I keep a number of tracks that go from/to places of interest. They can be loaded up (overlapping if desired) when needed. The tracks can be saved, downloaded, and imported into Google Earth. You can make tracks in Google Earth, translate them into gpx format via something like GPSbabel, and then upload them to the N810 and into MM when needed.

Coming from a GPS - hiking, biking, compile my own maps kind of use, I initially frowned on the "map tile" approach. But, 16GB of storage and a little time spent downloading pretty much solved that issue. I've found MM to be the most useful mapping app on the N810, at least for what I want.