They were great cars, several cuts above the Beetle.
Their primary problem was drivers ignorant of the handling dynamics of a rear-engined car. Any lifting or braking in a corner could easily bring the rear end around. You had to keep the power on and modulate with the throttle, somewhat similar to a mid-engined car. For what it was, the Corvair was a magnificent handler, better than a Beetle and, in its time, better than a Porsche. The second generation was a great driver's car.