To route around traffic delays: Press either "menu > route info" or the traffic light/estimated time button, and then press the button with the arrows on it. That will calculate additional routes to get your around traffic and tell you the possible times.
There are several ways to store favorites. The best way is to add a shortcut to your home screen...long press on the home screen, select shortcuts, and then select Directions & Navigation. You can also use the Navigation app icon in your app drawer or on your car home screen to get to your list of starred places, as well as recently navigated to places at the bottom of that menu.
The navigation still seems to work fine for me when I lose signal (and don't deviate route), as well as when I get a phone call (but I'm on GSM 3G).