I don't recommend Navit (unless you're John McClain)
If you're thinking about getting a GPS system, may I recommend a commercially available system that is built for your specific location (like the United States) as opposed to the Free Software Navit, using the Open Street Map system?
Here's why you want to avoid Navit and OSM at all costs: it tries to kill you.
Everything is fine up until it decides that the best route would be to use the expressway. Now, ignoring local traffic conditions, this would seem like the best route ... but the path taken is a tad heroic.
First, it instructs you to get on the wrong parkway, then make a SHARP RIGHT using your handbreak and get on the expressway using the offramp.
Second, it tells you to take a SHARP RIGHT off of the expressway overpass and on to the local street.
I hope you have good shocks.
Navit: for those of us who want to be able to shout "Yippie Kay Yay, Mother'efer!" in our daily lives.