i see the same ppl every day on the way to work with their Garmins on, it cracks me up (dont get me wrong, i have one and use it when i need it, but i crack up everytime I see someone using one in their own freaking city)
I always have my gps set up and it turns on automatically when I start the car. I don't enter in the location for where I need to go unless I don't know where I am going. Having it always on helps when there is an unexpected traffic delay and you need to detour through some odd neighborhood that you have know idea if it will let you out on the other side.
I do use my gps a lot on the highway even to places I know where I am going just to know when I will be getting there. That is my favorite part. I like to watch the ETA drop the faster I drive.