I didn't take advantage of the credit glitch in v1.0 -- this was my first Gran Turismo game (I'm not a 'gamer' at all) and I thought if I did that I would completely ruin the point of the game, which I thought at the time was to progress through the game with racing wins which would give me credits to purchase the cars I want/need for future events.
Now, however, I kind of wish I would have at least bought myself a few $20,000,000 cars with the credit glitch. I'm not a grinder. I can't even place 1st in the Red Bull events/Vettel Challenge. So, I've technically progressed well through the Career Mode and now I'm a little upset that the $15,000,000 Miura is the most expensive car I own (my balance is $11,000,000). It doesn't look like I'll be purchasing any $20,000,000 cars in the near future.
I find it so strange that there are so many people who complain that this game is "too easy" and "not challenging enough" but a lot of those people are also the ones who bought almost every car with the credit glitch and if they could just be given every paint chip or other bonus item for practically nothing, they would hop on that opportunity in an instant.