My portable GPS, sitting on the dash, BARELY gets a signal. The heated windshield is like a metal screen and it's hard to acquire 3D position. I'm assuming that the nav equipped ST had a design where the GPS antenna on or just under the dash plastic. I'm assuming they decided to move it?
As far as the NAV unit is concerned, if that's the same unit as in the Explorers, I don't like it. The screen is too small.