I mostly play multiplayer, so I can't comment too heavily on the AI, but I will say that it's definitely a lot more fun to do Free Play races, especially multi-class events. I had a couple of old IMSA-style presets saved, so after loading them up, and making adjustments to fit some the new cars that were added, I ran a race at Laguna Seca and had an absolute blast. Sure, there were a couple of cars that became impossible to catch up to, but I ended up getting in a 3-way battle for 3rd in GTP that ran for quite some time, and that was oodles of fun, especially when we started getting mixed in with slower traffic.
That being said, my main issue with the AI now is that they're sometimes a little too hesitant to go for passes on other cars, even if the car they're passing is in a slower vehicle. After the first set of pits in the same Laguna race, I ended up catching up to and passing a GTP car that was "stuck" behind an R8 GT3, and had been for several laps. If they can iron that out, and the AI occasionally having a little too much grip on worn tires, then it would be absolutely perfect.
Also, I'm not sure how many people here run the Spec GT2/GT3 races on multiplayer, but the refreshed BoP for GT3 is much better than before. The tire friction changes have made the cars much better to drive, as it effectively gives all of the GT3 cars an extra 15-30mm of tire width. There was an overall loss in acceleration and top speed, but the friction buffs are actually a very noticeable net positive for the class. It's espescially noticeable on the '23 911 GT3 R, as that car was downright terrible to drive beforehand. If you found the Spec GT3 cars awful to drive online before, I highly reccomend giving them a second chance.