Perfectlap has a good point. It is tricky looking at the screen when driving in an unfamiliar area. The good thing is that you can always just pull over and check things out if you need to. I think the bundle of add-ons and features out-weighs the drawback of not being on the dash.
My wife has a portable GPS on her dash and it definately is easier to look at while driving, and its nice to have when in a rental car in an unfamiliar area.
