Another vote for "completely different" here. For me, it's not only been excessive oversteer and snap, but lack of stability all-around. Sometimes it feels as if my car is being bumped from the side or rear by some unseen force, and it DEFINITELY seems to be exacerbated when other cars are near me on the track. It has bugged me the most at the 'ring, but that may be due to the difficult and unforgiving nature of the track in general.
Going to do some tests on Trial Mountain with a very stable FF car that is already set up for the track. The TRIAL Celica SS-II
PB offline (Practice mode, Racing Soft, 338 HP) = 1:26.479
EDIT: TEST RESULTS FOLLOW
***Above time was posted in Practice mode before tire wear was enabled***
Currently I can manage very consistent low 1:27.xxx and break into 1:26.xxx with a good lap in practice mode. Also, tires seem to last and last.
In my lounge I can manage 1:28.xxx at BEST. The car does not feel the same, it's more slippery. The tires are starting noticeable wear after only 3 laps. I think the tire wear issue is not coming from something different about the tires themselves or the wear model, but from the fact that the car is always sliding. Something is DEFINITELY different with the handling model.
I have a weekly race with the same group of people every week, and everyone has noticed that there is no point in running anything other than racing soft tires, because the hard/medium tires wear out EVEN FASTER than the softs. This can only be because the car is sliding more. In our first race, I had no online experience, and started with racing hard tires on a JGTC NSX, the Premium Raybrig model to be exact. The track was Suzuka Circuit. I had run PLENTY of tuning laps and had everything dialed in nicely. When I got out on the course, it was like I was on ice. The car could not hold a corner AT ALL. I pitted after 6 laps of this and put on a softs. I was 39 seconds down on the leader. The rest of the race (14 laps) I did on that one set of tires, and while they wore down, they lasted, and I was only 12 seconds or so back at the end. So I KNOW it's not my driving, it was the tires.
Another issue popped up on my Trial Mountain test that I did not expect. Not only does the car seem to handle very differently, the track itself seems different. Turns pull you in/push you out differently, and bumps that didn't pitch the car before do so quite violently now and some vice versa. The surface almost seems to made out of a different material. (I suppose this would also account for the lack of traction and handling woes if it were the case.) Also, you cannot rollover. I thought maybe it was this "anti-roll" that was affecting the handling, so I dropped the car's anti-roll bars way down. It seemed to help the issue a bit, but made the car sloppy just like it would in offline mode. I am at a loss.
Cliff Notes: It's different, I don't know why, and I don't know how to fix it.