I haven't played Gran Turismo 4 since 06. I played the GT5 (demo - not prologue) on my brother in laws PS3 the other day.... Wow, I need to go through the license a few times before I do the regular races. I got 1 min 57 seconds, 10 seconds slower than the online record. Of course, that was my first time I played in 2.5 years, I have a lot of practicing to do.
This game isn't for people that lack dedication. If you want 100%, expect to spend at least a year (consider you play more than 4 hours a day).
That list of Camaro's....wow. I can't wait to play this game.