Let's see... the 2007 Prius gets 60/51 mpg for $22.2K. Far better performance for slightly less money.
Shit, the non-hybrid 2007 Nissan Sentra gets 29/36 with the continuous variable transmission option, pricing out to around $16K.
Sorry, GM. I know you've got twice as many retirees as employees, but you'll just have to do better than that.