[aerohead]

I apologize for delay on this one,as at Cd 0.188 the EV-1 has generated a great deal of interest at the Aero Forum.
My interpretation of the photo,is that the car does suffer flow separation over the backlight and boot,as the smoke overides the structure and initiation of turbulence is evident with the swirling smoke trace.
In GM's defense,from previous articles it has been reported that GM has very stringent and rigid internal standards for outward visibility for the driver which may have precluded the use of a more gentle angle at the rear.
Aerodynamically,the tip off would be the metric of the car at Ft.Stockton,setting the LSR,where the "Yellow Ferret" aluminum boat tail cone is used with an included exit angle of 9-degrees,which when measured from tip to roofline,gives the back of the car a 15-degree angle,oddly,not as radical as the Mair' 22-degree aggressor.