Temple University Economics Professor William Dunkelberg recently posted a nice, succinct article on how GM really didn't repay us after all.
He explains that the $8 Billion that GM gave back was clearly nowhere near the $80 Billion of TARP funds US taxpayers "invested" in GM and Chrysler. Instead, taxpayers received 61% of GM ("and a block of stock for the UAW").
Dunkelberg slams GM by saying that such a loss hardly represents the returns necessary to drive up the stock price "needed to insure a return of taxpayer money", hinting that he really doesn't believe GM will be able to pay everything back.