PRO: First impressions, physics feel much improved compared to GRID 2, much more like the original GRID, certainly no Assetto Corsa which I don't think anyone thought it would be.
CON: For some reason, at 900 degrees of rotation, the wheel feels extremely slow, I can't believe in a game as modern as GRID Auto that we still don't have proper support for a 900 degree wheel. I had to lower my DOR to 360 in the Thrustmaster control panel which feels pretty close to 1:1, 540 DOR also works but you will have to turn the wheel quite a bit more to get the response you want. 900 DOR feels like you might as well be Rally driving and having to spin the wheel all the way around to take any turn.
CON: FFB is meh, I'm still trying to find settings I like. It has a vibration setting, strength setting, and wheel weight setting. The default setting is 50/100/50 which feels awful on my TX. Way too heavy and very unresponsive, a lot of shake in the steering wheel which feels like a cobble stone road. The vibration setting controls the road and curb feel, I turned that down to 20%, anything more feels like cobble road even on smooth tarmac. I like my strength setting at 60% but this one will certainly vary with preference, but anything above 60% starts to feel like clipping to me and becomes too difficult to change directions quickly. The last setting, wheel weight feels like friction when releasing the wheel, at 100%, the wheel feels slow to get back to position, at the default of 50%, its not bad but I prefer a little less at 40%. At 0%, it feels like the wheel isn't attached to the car, just very floaty with little resistance. So far, 20/60/40 has been best for me.
CON: I haven't had time to try all disciplines and cars, I played with the Tuner discipline a bit, mostly muscle cars. The rear end of those cars will step out pretty easy if you stab the throttle coming out of a turn without any assists. Gently squeeze the gas pedal and you'll get a smooth lap or learn to drift like a pro. After trying some more cars, it seems all rear wheel drive cars are all like this. AWD and FWD handles pretty well, but RWD cars are a handful and the rear end breaks loose constantly.
EDIT and UPDATE: I previously said the FFB was meh, but after more time with it and getting it adjusted where I like it, I can honestly say it feels very good with my Thrustmaster TX. I like 30/70/40 and it gives a good feel on all of the cars. This game is the first racing game/sim that I've ever actually enjoyed drifting, the FFB is so good for drifting.