Here is the my best "guesstimate" as to when C7 customer cars would start shipping: Approximately September 20th (two weeks from today). This guess is based on two non-confirmed factors, and there is a final "caveat".
Factor one: GM has announced that they will be doing the usual new model "quality hold" on the C7's. A quality hold gives GM the opportunity, that if they later find a systemic part quality problem (as happened in the quality hold for the new C6 Z06's), to not have to chase the cars all over the country, instead fixing them at the plant. A quality hold can typically last between two weeks to 30 days. Since almost every one of the 4,000 parts in the C7 is new, most believe that the Bowling Green Assembly Plant (BGAP) will employ a 30 day quality hold on the C7.
Factor two: There is limited secured, fenced space at the Bowling Green Assembly Plant (BGAP) for the quality holds. That pre-shipping space is limited to a maximum of 900 cars.
The "Caveat": Let's assume the above two factors happen to be luckily accurate. This would mean, since the recognized first day of C7 customer car assembly was August 21st, that shipping might start on September 20th. HOWEVER, the caveat is that BGAP Plant Manager Dave Tatman has stated that the Plant will not ship cars with a known problem. The exception might be for a small, small issue that could be addressed simply and easily by dealer's when they are doing their required PDI process (such as a replacement of the left rear fender reflector due to a lens visual imperfection). A major delay would infuriate those who want and expect their cars really soon, but GM knows that the world will be microscopically examining the new C7 for any delivery flaws. Hence Dave Tatman would keep the cars at the plant IF a major quality issue were found during the extended quality hold. For those who might consequently go ballistic, those folks should ask themselves, "how much faith do I have in my local dealer's service department (which has not even seen a C7), to fix a significant problem." Again, all this is conjecture, as NO KNOWN QUALITY PROBLEMS EXISTS AT THIS TIME. Hence, my guess remains that, a guess, that in two weeks the transporters will start rolling.