Awesome work on this thread Nick.
The Bluetooth Phonebook - This is something I've seen quite a few times on various pairing devices that download the phonebook.
Navigation Icons - the iGo software is quite tweakable. The guys on the Avic411.com forums have done massive overhauls to it. And GPSUnderground.com has lots of info on the config files.
Noise - Jeff's theory on the line level is a very valid one... be interesting to see if someone tries this before I get my unit.