While the number of miles it shows for range is wildly inaccurate on the highway, the navigation does not seem to be impacted by that. When I've been unable to make the next charger, it has warned me a good hour ahead of time, and slowing down by 10-20 MPH has given me the range I needed. I've never run out before hitting a charging station.

I'm in agreement that I think they are terrible for most rental car needs.