After participating in the closed beta I came away excited, but a bit disappointed how much was carried over straight from GT6.
Now that I have just had a go at the public beta, all I can say is, Wow!
I just ran the 6 laps at Interlagos mission challenge in the Mazda Atenza Gr.3 with fuel and tire wear, and I was very surprised with how challenging it was. The first time I tried to run 4 laps on fuel map 1, and ran out ~100 meters before the pit entrance, and lost ~10-15 seconds because of it, finishing 12th. The second try, I came out of the pits right next to the lead Audi R8, and diced with him back and forth for the last 3 laps, before overcorrecting and spinning with just a couple corners to go, finishing 8th. On the 3rd try I came out of the pit stop cycle ahead of everyone, but in the last two laps the second place car closed the gap from 3 seconds to 1 second by the finish, as I opted not to change tires. I can only imagine doing a similar race, perhaps 2-3x longer, in an online lobby with a bunch of similarly skilled drivers is going to be heart-pounding.
The improvements to the AI, removing the steering limiter for pad users, updated tire sounds, sounds of the chassis and drivetrain, and excellent graphics (I am on the standard PS4) all add up to what is without a doubt my favorite Gran Turismo yet, and I have played through every GT game since they came out in '97. I haven't even started on the Scapes, Livery Editor, Brand Central, etc, which I honestly expect to spend almost as much time in each of those as actually racing.
I gave up GT5/GT6 when I sold my G27 and PS3 to buy a PS4 in Oct. 2015 when they announced the original 'public' beta was coming, and it has been a long 2 year wait to get back to the series. But after my experience in the beta so far, the wait seems like it was well worth it. Now if I can just manage to get a new wheel for the PS4, and maybe an HDR TV!