I've done a lot of laps at Road Atlanta, so I threw together a quick comparison from one of my videos. The RX-7 I'm using in AC is modded to match my actual power curve and suspension setup. The video isn't fantastic quality but it gives a general idea of the flow of the track:
First of all, the track drives very well in general. It was pretty easy to get in the groove just by recalling my real-life experience of the track. Pretty much all of the visuals are spot on. I'm already having more fun with this than with the iRacing version of RA.
Assuming it's useful for future updates, I'll give some turn-by-turn feedback:
Turn 1: The sim track has a slight hump on entry that shouldn't be there. Not too noticeable though. The corner also feels a little too flat in general, it should climb more - I think LilSki confirmed that the front straight is too high relative to turn 1.
Turn 2-3: Really good. This is a tricky section in real life - trail braking while cresting a hill - and it feels right in the sim.
Esses: The right-hand corner in the middle of the esses seems to jut out too far. AKA it seems like I have to keep driving too far to get to the apex. I think this part should be straightened out a bit, but the lidar data or a satellite image should be able to confirm.
Turn 5: Spot on. I think the exit curbing could be taller / more bumpy. Notice how much more my real car bounces when I run over the curbs there.
Turn 6: In real life, turn 6 feels like a bowl corner throughout. In the sim, it's more like hump-bowl-hump. This would need to be smoothed out a bit.
Turn 7: Spot on.
Back straight: Spot on.
Turn 9: The grass juts out too much on the inside edge of the track. In real life the grass on the inside edge follows a smooth radius around the corner.
Turn 10a/10b: This section is especially good. The visuals entering here make me feel like I'm actually at the track.
Turn 11: As others have mentioned, this is the biggest error. It's easy to see in my video comparison how long the sim track keeps climbing while I'm going down the hill in real life. If this gets fixed; this track will be very high quality, despite the other minor issues I'm listing.
Turn 12: Seems ok, maybe a bit too flat. But it's hard to tell since turn 11 is so far off.
Like I said, it's a very good track mod in general. With a few tweaks it could be great.