I've not tried this but there are some parameters relating to zoom level in map download. I wonder if that can yield you a smaller map file size.

waypoint/navicore (default map application) uses the 700mb east + 700mb west coast us, etc. maps.

Maemo mapper does not use these (despite the misconceptions in many threads) - maemo mapper downloads tiles from sources such as openstreet, google maps, VE (best IMHO) and yahoo maps. Unfortunately google for instance has taken measures to prevent downloading a large amount of tiles at once (those python scripts floating around don't work anymore) and the databases are stored in /home/user/.maemo-mapper/ You can determine the size of the saved maps by the command $ du -sh .maemo-mapper/ (in the home ~ directory)

Also while maemo mapper doesn't do rerouting per-say I have found that if I take a detour and then return to the path it'll direct me once again. Also the way it does routing is that it connects to a website that generates the routing in the proper format which it looks up via google maps. Thus the need for an internet connection. It's unfortunate that there are so many licensing issues with maps.

1.8gb? I just recently did a build on the upper north west and it came to almost 8gb. If you're talking about the vector maps, that's a different story though. But still, 1.8gb isn't bad considering all that's packed into there.

i downloaded navit and i cannot figure out how to view maps on it. i already downloaded maemo maps and maps of georgia from http://downloads.cloudmade.com/, but i cannot view it on navit.