You will be glad you got them!!! Thankfully I'm not a germaphobe or anything like that, but having ridden the train from Jacksonville, FL to Jesup, GA once, and to Charleston, SC a few times, I can tell you that the restroom situation is usually not amazing, and certain odors may permeate the entire car depending on who is in it and where your seats are located.
I've always ridden by myself as a young adult visiting friends and family, and when you have a stranger sitting next to you, it is always a good idea to have something to occupy yourself with - usually a good book for me, or my portable DVD player.
It is usually cold - I've ridden in July and November and both times it was freezing. In July I actually got out my bag (I always just carry it on) and pulled on sweat pants and a hoodie over my tank top and shorts and was still chilly, but I do tend to run cold.
For me, the seats are not at all uncomfortable, but I have heard horror stories of old and damaged seat cushions, etc, that made sitting for upwards of 6 hours unbearable. Some people like to bring a seat pad, it just depends on how much cushioning you like.
That's all the tips I can think of for right now having ridden the train a couple of times, but I usually just fall right to sleep between stops. Hope some of this helps!