Not electric, but my family has a Subaru with lane assist and adaptive cruise control. It doesn't liberate you from driving the car, but it makes driving a lot less tiring and aggravating. Like @Mike N says, if it doesn't like the signals it gets from the sensors, it dumps you back into manual mode.
What I tell people is that it's like another person is driving the car, and that person is a teenager.
In other words, you still have to be alert. Between the different controls, my favorite is adaptive cruise. I can just get behind a semi going 70 MPH on the freeway, and sit there forever.
To replace our other car eventually, we're seriously thinking about a plug-in hybrid that can be driven locally on full electric. It has to fit an upright bass.