My own 2¢:

Having known several people with cars that have built-in NAV ability, every one of them wound up using their cell phone or a standalone GPS device. I use a 2013 Garmin when I travel and it is far superior to most of the built-in GPS devices I've dealt with. The biggest challenge to any GPS device is how updated its map software is. At least with a detachable GPS or a smartphone, you can chunk it and get a new one when it is too obsolete to run the newest/latest/greatest revision. With a built-in system, you now have a fancy piece of panelling with movable pictures on it. Personally I wouldn't waste my time or money installing a built-in NAV system on a 13 year old car. How useful is your 13 year old cell phone, or 13 year old laptop? The GPS device will be similar in its antiquation.