I'll add on to mine:
1. Visibility. Excellent sight lines to the right when I'm backing out of the driveway.
2. BT integration. Pulls my substantial list of contacts in from my iPhone effortlessly and call quality/sound is excellent.
3. Send destination to the car via Google Maps. Beats the heck out of entering addresses.
4. Included traffic conditions and dynamic rerouting. Sure it's available on a $150 garmin so it should be included in a $2000 nav package (but isn't in many cases).