Frequent Amtrak rider (Lincoln Service (CHI-STL) and (CHI-MKE) primarily) here. Looks like you'll be on the Crescent during a largely overnight segment, which is good. A couple things to expect:
>the atlanta station really sucks, it's not in downtown nor is it connected to MARTA, and the interior looks like a small municipal airport if I had to make a comparison
>your trip is overnight, so pack some melatonin and the ride quality won't really matter
>your train WILL get delayed, so expect to get in a little later
>The people on amtrak are usually pretty nice, especially the staff
The ride will definitely be more comfortable than an airplane too. I'm 6'5" and always take amtrak whenever feasible because I simply don't fit in airplane seats (at least my legs don't).
Don't compare it to european trains too, you'll be extremely disappointed. Go in with low expectations and you'll be pleasantly surprised.
