I have a 2004 VR with the factory nav unit. I see that the nav for the latest V70 includes "real-time traffic". Does this new nav unit use real-time traffic to re-route? Are there any disadvantages to the new unit? Does it still measure the car's speed and direction using wheel rotation and a gyroscope to update the car's position when one is out of contact with the satellites? Is it feasible to upgrade the old unit to the new one? What would be involved? If the old unit malfunctioned and needed to be replaced while covered by the Volvo Increased Protection extended warranty, might I be able to get the old unit replaced with a new unit if I were to pay the difference in cost between the old and the new (including the cost of whatever software update might be required)? What is that cost difference? Has anyone tested or reviewed the new unit? Is it better enough to be worth pursuing an upgrade?