I have to be honest though, as much as I love Google Maps, whenever I'm driving, I use my in-car navigator that Volvo use. I find the traffic conditions update quicker and are more "local", since traffic information is broadcast in digital format over regular FM radio stations, the car picks up on it and adjusts/warns accordingly.
Google on the other hand takes quite a bit to update a route based on time/traffic.
For average travel times, when trip planning for instance, Google wins hands down.