Ah, I've just started looking for something like this.
My LCD sits pretty low in the car so it's a bit distracting to look down at it all the time while driving, so I'm putting a VFD higher up on the dash that I want to display song info and iGuidance stuff.
In addition to current and next street, I wanted the VFD to be able to display the direction of the next turn, and the distance to the next turn.
Would it take up much processing power to update the distance to next turn once or twice a second? I won't have time to play around with this till the end of this semester. I can't imagine it'd be very difficult read off the distance to next turn if you've already coded for the streets.