Last I have heard Google's system is not really focused on solving perception problems, especially in inclement weather. They are waiting for the research community to catch up.

The perfect conditions they drive in allow for very precise localization against a detailed (sub-cm accuracy) map of everywhere they will drive which includs pre-marked stop signs, light, cross walks, etc.

To say nothing of snow.

Cars are already better at navigating snow by themselves than with people at the [direct] controls. Traction control and drive by wire are common.

True, but car can't see lane marks and can't even recognize where the road is once it is covered in snow.

Neither can people, but computers have the ability to see through the dark, rain and snow. They have the benefit of GPS. They have the benefit of being able to work with embedded sensors in the roadway (which to be fair is in its infancy, but you know that's where it's going).

I like people a lot, but I would not bet on a person driving better than a computer. Our reaction time is way too slow and sensory input very limited.