Okay, so just out of curiosity I rented GT6 to try out.
My impressions are basically this. GT6 is what GT5 SHOULD have been!
1.) Overall the game looks gorgeous! This is quite possibly the best lighting system I have seen on anything on PS3 and about the only thing I can think of that I've played that looks better, lighting wise would be Killzone Shadowfall on PS4. The lighting/shadow detail is quite striking, especially during evening or early morning races! Car detail on the premium cars look fantastic. Hands down the best car models I've seen on any console racer. Where the game starts to stumble graphically are track textures, car shadows, and overall trackside detail. It's a definite improvement over GT5 but I have a feeling that Polyphony pushed the PS3 capabilities about as far as they can and that's about all you can ask for.
2.) The handling and suspension of the cars, massive improvement over GT5! Now the handling feels so smooth, so natural! If I had an actual steering wheel it probably would have felt even more so! I have zero qualms with the handling system. It's spot on as far as I'm concerned.
3.) Car sounds, yes this has always been a complaint from GT players and sorry to say there's no massive improvement here. However I will say that if you have a home theater. Go into the sound options and enable either large or small home theater and then choose your set up (either 5.1, 6.1, 7.1, etc). I will say enabling this showed a BIG improvement in the engine sounds in the game. Still not great, still not where it should be, but better!
4.) Arcade mode has been improved quite a bit in terms of track selection. There is quite a large initial selection of cars and tracks from the get go, including several rally/off road tracks and go kart tracks. Not a bad selection at all for someone who just wants to jump in and start playing. Career mode, I barely got into last night because of time but I'll edit my impressions later when I get chance to play more. Also I didn't get a chance to play online yet so I'll edit that as well.
5.) Opponent AI, dumb as ever!!!
Overall I would say GT6 is a good but not great game. Unfortunately it's still missing some features that I feel it needs to have in this day and age such as a meaningful damage system, car customization, better engine sounds, better opponent AI, etc. However overall, for what it DOES do it does very very well!! You can definitely see the work that Polyphony put into this game and it HAS made strides. However it still has a ways to go to get this franchise back to the greatness it once was. Right now, based on what I've played I give this game a solid B+.