To answer the OP, I worked with Jeff on one of my warranty issues and did not get anywhere. After several PMs it went from Jeff saying "give me your contact information and I will setup a case for you...I can get that case number for you shortly"...so I did...and one of the following PMs was "have you tried contacting customer service?" I thought he was customer service.
I never received the case number. At that point I quit corresponding with him. I honestly felt like he was not with GM and just trolling for personal info. Don't get me wrong Jeff presents himself as a very professional, courteous and articulate person online and I would presume that he is the same offline and maybe he is legit. But does anybody actually know this person? And if he is legit then what's the point...give us hope that GM is actually listening only get the run around. Just a bummer.