Quite a bit of information from the VoltNation meeting has been mentioned in comments or on other posts, but following is some other information that I haven't seen mentioned yet.
Apparently this vehicle will be based on the Delta II platform. The Cobalt is now based on the Delta I platform. I am told that the Delta II platform is bigger than the Cobalt, but smaller than the Malibu (Cobalt I believe will move to the Epsilon platform in the future). The height of the roofline should be a few inches higher than the concept model.
As I looked at the concept vehicle, I didn't see where the large flow disturbances were that would give this car a poor drag coefficient. It looked fairly streamline to me. When I asked about the aerodynamics, the answer is that they needed to reduce turbulence and smooth the airflow from the concept. The design is still being refined as they finish components, but I did not get any number for a drag coefficient. Since the corvette has a Cd of 0.28, I would expect a number that is lower for the Volt (I think the EV-1 was something like 0.19).
From my various interfaces with the GM engineers, it is my impression is that a lot of attention is being made to make this vehicle efficient. Performance is not the priority. A lot of focus right now seems to be on low drag, low power consumption of auxiliaries (they might include an "Econo" setting for the AC), and system integration. With all the various operating scenarios, cold weather and cold batteries, hot weather with high AC load, regen braking after a full charge (for those who live on top of a hill), and other such possibilities, GM will probably need a great deal of computing power onboard to assess all of these situations and determine the best mode of operation.
From all I have read, they have successfully done this with the two-mode hybrid, that provides seamless power with both engine and electical power, so hopefully they can provide similar results for the Volt.