I have a Garmin nüvi 2598. One of it´s features is an alert when I exceed the speed limit. I find it kind of useful. Usually I do not use the routing feature.
Cross county out-of-date maps are often ok. Prominent features like mountains do not change fast enough to make a difference.
OTOH out-of-date city maps are more likely to not even have the intended destination on it. That can make navigating a little hard.