I think if you don't have GT5 and want a GT game, GT6 might be good, otherwise it's up to you, if you want to invest into it. I guess it'll be worth it later, when more of the tracks come out and they make another special edition with DLC's. But that's just my guess. Sounds are a slight improvement, but if it's gonna be ok at all cars in full game, who knows. Physics are better, the bodyroll at Leaf caught me totally unprepared, but the overall handling is close to GT5, though it's bit better.
I still don't get how the FFB can be so strong; maybe to compensate for the numbness, but even on weakest setting it's unbearable, after 1 hour i had to take a break, because my arms hurt.