Google Maps misses downloading facilities so you can,t navigate as soon as the network is gone. They could use his skills!!
I have installed Maemo Mapper on my N900 and the UI is done very nicely. You can find it here:
http://my-maemo.com/software/applica...38&fldAuto=814

I did not try all fuctions, but the basic fumction, showimg your position on the map, worksfine, zooming is fast. I used MM on my N810 and the menus are more or less the same, so parts of the UI are not adjusted to Maemo 5 standards. They work fine though, as far as I can tell. Flite is a program that is missing by now, so you can't use 'spoken directions' to navigate. In that field you should not expect much, just a line on the map. Right now it is far better than OVI maps , that lacks any advanced fumctions above showing where you are on the map. I would give it a try!