Must get back to play more, no time to write a review...
In short words:
This game is a big positive surprise. There's some minor bad physics similarities to GT5P, but they really are just minor things. The game feels like "back to the roots" in my opinion, with much better graphics and physics (i really like it with the G25, almost perfect feeling).
I don't care if the physics underneath are not the most detailed ever. It just feels great.
Tried a stock S2000 in training mode (where you can really turn off all aids). Feels very good, drifting too (as i said, it's still a little too snappy like GT5P, but much improved now in GT5). Reminded me of the trackdays in my S2000 a little bit (as much as a video game can replace reality (which it can't right now)).