Bruce has one in his truck (I'm not sure what brand), but it is great for him. He is a realtor and uses it to show properties. He can program in various addresses and it takes him from one to the other.
Yes sometimes your info disc isn't up-to-date, but overall it's great!
We want to get a portable one that we can take on the motorcycle and the boat (and I'd get to take it in my car)