There is a warning in the manual about sharp corners. There are times when on coming cars could look like they are in your lane.
The biggest issue is that it ignores stationary cars, so if you come around a corner to red traffic lights it would drive straight into any stationary cars. Which is why I only really use it on the motorways (highways).
A really rolling road (Arizona has some of these) where the car might be one "roller" ahead of you but look a lot closer, then your car hits the brakes at the apex with a car tailing you.