I start working with google last month on vehicle that is capable of sensing its environment and navigating without human input.
That is awesome - was it scary at first?
There is nothing about it to make it scary. Many techniques were asopted  to detect their surroundings, such as radar, laser light, GPS, odometry and computer vision.
Do you ever feel like you would rather be in control yourself?
If you want a stress free drive, you should consider an autonomous cars. They have control systems that are capable of analyzing sensory data to distinguish between different cars on the road.
Are they very expensive? I have never really looked into one.
Well, not really when we consider their benefits such as significant reduction in traffic collisions; the resulting injuries; and related costs, including less need for insurance.
I really think that they are going to start becoming quite common in the next few years. Are you thrilled with yours?