Earlier quoted context omitted.
They're the present here in SF, driving every day and more safely than the humans do. And as a human driver, I can testify that these streets are not particularly easy to drive on.
They are here in the Phoenix area too and I have not seen and issues with them. However, we are blessed by sunny weather 99% of the time. I think the biggest challenges will be having them drive in adverse weather conditions present throughout the rest of the country, such as blizzards, hail, torrential rain, dense fog.
It is also funny to watch them get stuck behind busses, having followed too close to safely go around them when the bus stops to pickup/dropoff.
Also Ive seen multiple instances of them trying to turn left on red and pull far enough into an intersection to cause issues.
Finally when I am on my skateboard they dont seem to recognize me as they drive very very close and fast, though I havent felt risky enough to really test this.