I played a demo at the Petit Le Mans. The scenery was beautiful, the cars were pretty good but not quite as good as the premium cars in GT5 (at least on the track).
What I really didn't like though was the driving. It felt just a little sloppy compared to GT5 and not as precise. I would slow down enough for a turn to where I thought I would be able to take it no problem, then a second later I'm off the track. They even hooked us up with the Fanatec Forza wheel which was really nice, but that might just be the wheel or the sensitivity settings that caused it. I guess I just need more time with it.
I also got the chance to spend time on an iRacing sim... now THAT is what I want from a racing game! When it comes to the driving experience and the realism, iRacing > anything else