I just wanted to make a few observations about Navit on my N800:

I have Navit up and running with the UK OSM map. It took some effort and fiddling, but now I have everything set up for easy tweaking (see my method below).

I am using an external GBS bluetooth (cheap Holox bought on eBay - fast and super easy to connect)

The map display speed is a little slow compared to dedicated GPS devices, but not bad at all.

MiniGPSD vs. Built-n GPSD
I have miniGPSD installed in addition to the built in GPSD - but although miniGPSD can easily connect to my BT GPS, Navit fails to recognise this connection and offers to start my built-in GPSD instead - which fails as miniGPSD is already connected - Reboot required to get everything working again! Much time wasted experimenting - finally given up with miniGPSD unless anyone can advise a way to configure this to work (alternative port to standard 2947 ??).

Navit starts and stops the built in GPSD just fine.

Flite
Flite works (with the much mentioned poor quality voice - but at least it works) - I already had Flite installed for Maemo Mapper, so just had to uncomment the flite line in navit.xml

Display
The OSD settings suggested by DWould on his blog are a good place to start, although his button for gui.fullscreen() does not work so have disabled it until I can work out what is wrong. Also - city and street text-sizes all need to be enlarged to 15 as a minimum to be visible at a reasonable scale.

Configuring and testing
The process of trying/editing/trying/editing was extremely tedious until I worked out a better way - copy navit.xml into a folder on mmc1 and use leafpad to edit it there. Set up Personal Menu to run Navit with the xml file as a parameter (navit /media/mmc1/Navit/navit.xml in my case). Create a link in Personal Menu to load the file into Leafpad for easy quick changes. Keeping the xml file on mc1 has the additional benefit of it being easy to pop the SD card into my desktop machine and load the xml file there for full large screen editing. This setup works for me - I may streamline a little more by using xml include statements and swapping out key areas of the file for specific edit tasks.

I run Navit with pitch=15 to give a moderate degree of 3D look-ahead, whilst keeping it finger flick friendly for punching in destinations.

Bugs - unfinished work
The destination entry system appears to be broken - or maybe my UK map simply lacks the correct annotations to allow me to enter place names with decent results. e.g. - I enter (very slowly to allow the db to keep up) in the City box: Dor (to search for Dorking) - 4 entries pop - tiddly little places show up - but definitely not Dorking. Hopeless.

And what are the Map, Bookmark, and Destination buttons supposed to mean? This has been mentioned before so I am only repeating my experiences.

Using my fingers to move around the map, I can bookmark places and these are then available to be set as destinations at any time - this works very well.

OSM maps
The level of detail on the UK OSM map is pretty amazing. Not as good as on my main car GPS, but not bad at all - I am impressed. It is certainly good enough for most of the journeys I make.

Finally...
All in all, I am blown away by this application and deeply grateful for the work that has gone in to get it to the state it is right now.