I use the nav all of the time. Although the user interface is quite clunky at first, I have gotten somewhat used to it.
I also get entertainment value out of some of the strange routes it picks in Bergen County NJ where I live. It's fun to watch it "think" each time I ignore a turn it wants to me to take, and to see how long it takes it go "get with the program" and recommend the route I was going to take anyway. Of course, this entertainment value may be because I am a computer geek.