Just tried this "demo" today
First impression: mixed.
The design is quite cheap in my opinion, and the "advises" from Lucas O. that appear in blue text already gives a feeling of a 15 years old game. That's nothing, but it gives a first bad impression
Then I raced: OK, as advertised, the feeling of the car is very nice, with the car moving a lot from right to left in the turns (a little bit too excessive in my opinion, like in forza), and the feeling of the tire grip is amazing. BUT, I don't know how to say it exactly in engligh, the graphics are NOT SMOOTH at all, a feeling of "lags" and "image shaking" which is absent in GT5 for me (running on a slim PS3). Very very annoying. Second, that's a detail, but boring anyway, I cannot set the speed in km/h, it is in miles/hour; that's not too bad (but strange); but at the same time the car's speedometer (in the interior) is maxed at 180km/h, so on the straight line the meter already hits the upper boundary, not a real problem but come on, they include two cars and the quickest car's speedometer stops at 180km/h, already a bug or is that true in the real 370z (can't believe it). Same problem with the exterior view in the leaf: the speedometer stops at 80 (miles/h) but the car goes above, so silly.
I fear a lot for GT6 for the moment, but anyway, as many here I will buy and play it a lot anyway :-)