One interesting doohickey that accompanied us on our journeys in and around Chicago was Hertz's NeverLost system. It's the Magellan-powered built-in GPS system that is helpfully available (for an extra charge, of course) on Hertz rental cars. Here's a review comparing it to Avis' solution:
NeverLost does tend to make a dummy out of you. My Mom and Dad used to be amateur cartographers, blithely trekking into unknown lands with only courage and a road atlas to guide them. With a GPS system plotting the course, though, you almost feel like you're a zombie - after the end of the trip, you have zero idea where things are in relation to each other.
The most interesting flaws in the NeverLost system are the ones inherent to GPS. In the covered roads and underpasses that slither through Chicago, you will lose satellite contact for long stretches of time, which makes the automated voice-direction system go haywire. Additionally, the system may not be able to discriminate between two parallel roads that are very close together, which can lead to some mishaps.