Many of the posts I'm reading suggest voice command on this unit is for ipod and phone only. Another poster noted reading page 146 of the manual and seeing instructions for using voice commands with the navigation function. The manuals were posted by yet another user here:

http://avic411.com/forum/viewtopic.php?t=15876

Has anyone that has this unit installed tried to give a voice command for navigation as documented on pages 146 & 147 in the manual to see what happens?

All it says is that you can call up the NAV screen from the AV screen by using the VR in the same way in which you can change sources. It takes a button push to do this so you might as well just hit the MAP button.

Ah. They are referring to "navigation system" as the entire unit, not the nav function of the HU. I did not realize that at first. Reading further, they list the phone and iPod features specifically. Oh well, hopes dashed.