Large vehicle GPS

Owned for 4 weeks. Drove 4,000 miles from Milwaukee to Phoenix & back in a Ford F250. With a Moonroof & the unit sitting on the cup holder I never lost the signal. On a F150, no moonroof mounted in the same position for about 300 miles I've lost the signal twice but not when mounted on the dash. Auto light dimming feature is excellent. The screen is extremely clear in spite of relatively low resolution. In a pinch it could be used in a smaller vehicle but not on the dash. Recalculating route is a little slow but not an issue. Occasionally indicates to make a U turn instead of going around the block & sometimes uses a road name instead of I670 etc. Internal speaker could have a little more volume. At 80% it was difficult to hear over a audio CD. Dead reckoning feature needs to be installed by a professional. But it is an OUTSTANDING GPS!