So I finally bought myself a laptop which came with Ubuntu Karmic Koala, and I've got the Nokia bluetooth gps unit working properly with it. I've managed to get JOSM's LiveGPS module reading data, recording traces and saving gpx files, but it gives some nasty errors at startup - I just tell JOSM to ignore them. I can get gpsdrive and Merkaartor reading GPS data, but I haven't yet managed to get any useful maps working for them. I'll play around some more later.
My basic learnings so far:
* You need to use the "-b" option to gpsd or else you confuse the Nokia LD-4W.
* You can't un-confuse an LD-4W by holding in the off-switch for 10 seconds; that just removes all bluetooth bindings.
* As per the manual, you un-confuse an LD-4W by holding in the off-switch while plugging in the charger.
* I didn't get the dongle reading gps data by using Ubuntu's Gnome Bluetooth Preferences - I had to edit /etc/bluetooth/rfcomm.conf (instructions are available online), then add the line
DAEMON_OPTS="-b -F /var/run/gpsd.sock"
to /etc/default/gpsd . I start my gps by doing "sudo rfcomm bind rfcomm0" and "sudo service gpsd start", and then it's sending gps data to whichever program requests it, so you can have many programs reading gps data together (at the moment I'm running gpxlogger and LiveGPS at the same time).