I've only had it for about five hours now, and I haven't even started GT Mode yet!! Well, I bought myself an MR2, but I haven't actually driven it yet.
Spent my time zipping a Golf around every available track in Arcade Mode first.
This game is everything I expected it to be! I know "Best Game Ever" might be a bit redundant, but I think it's the truth. So far, I haven't seen a thing that I would change. Sure, it might not be perfect, but it's far surpassed the expectations I've had of it for the last couple years.
I agree wholeheartedly that the Nürburgring is a hell of a tough track. My first hot lap was a disaster, I was amazed to get around in under ten minutes. I went back a little later with a Shelby Cobra, and gave up after a quarter lap (the car's so twitchy that the little bumps on the track will send you into a spin for no apparent reason.. hehe). Definitely my favorite track, though, it's the track I was looking forward to the most.
Other highlights: I quite enjoy the Infineon Raceway.. it's just.. fun.

And while the folks who played Prologue are probably a bit jaded at this point, I was totally blown away by New York. The sheer detail in the track is utterly astounding. And it's a lot of fun, to boot.
All in all, I'm VERY pleased with the game. It was everything I was expecting, and then some.
Did anyone else notice that automatic cars actually
behave like automatic cars? Someone on the PS.com forums was complaining about an "error" in the Mercedes SL500, that the car never came to a complete halt. If you stop the car and let off the brake, it'll start to inch forward..
just like a real automatic car. That's brilliant! Talk about attention to detail!

I'm assuming that at least some of the other automatic cars behave that way (don't have a McMerc, as I haven't played GT Mode yet).