Mike:
What's the GM equivalent to the Corolla? What is their car or similar size that gets similar fuel economy and stickers for $15K or less? Is it the Cobalt? If so, I think the difference in fuel economy between it and the Corolla would more than offset any savings in cost over 100K miles. Unless I'm badly mistaken, the Cobalt gets 6-8 less MPG than a Corolla, especially if you get the Toy w/ a 5-speed.
Please tell me I'm wrong--I wouldn't mind buying a Chevy if they make one that can compete with the Corolla.