The only way to gain credits is to win or place in races. I'm not a fast racer, but I can and do drive the cars. Since I'm not fast, I don't win or place, therefore I don't gain credits, so I won't ever have access to the cars I want (GTR cars) if it goes that route. I don't have time to be bothered with the stupid lessons, especially since I can't change the setup. Even the braking lesson, I set my brakes up very light so I don't lock em up. With default setup they are 500+ n/m (or whatever) heavier than I use, therefore I lock em up every time and can fail simply by poor braking. Therefore I can't unlock the cars with this system. So after driving the FZR (not fast, but clean) for a year, when full version comes out, I will be locked out of my favorite car even though I've paid my $44 USD and have been driving it for the past year. An unlocking system using distance driven or laps driven would be the way to go if they get locked back up. I'm working on 9,000 miles now since S2 came out. That's more than I've put on my motorcycle riding it at least 4 times a week this summer (mostly work commuting).
edit: BTW, I can't drive the F08, therefore I don't. Even if it is currently unlocked for me.