Toyota's DVD based NAV system is nothing to be excited about.
I'll assume the nav system is a close relative of the one in my 2008 Lexus RX350. That system finds a signal fast and holds it well.
Why it needs A DVD system stuck in the trunk to do less than a modern deck-of-cards-sized portable unit is beyond me.
Toyota, in their infinite wisdom, have disabled inputting destinations when the car is moving. (They didn't do the same for radio, telephone, climate ontrol, or any other system requiring driver input.) In compensation, Toyota provides a voice recognition system that may be the single most dysfunctional piece of Japanese technology I've ever seen. It's almost comical how poorly it recognizes what's said. It's completely unimpressive.
I wouldn't recommend paying extra for it (unless, like my RX, it's bundled with something worth having like HID lights).
Don