I once rode coach on the Silver Star, Baltimore to Tampa. It was right after President's day weekend, and no sleepers were available. This was almost a 24 hour trip. At the platform, I was assigned a window seat. My seatmate was a young mom who needed the aisle seat to keep track of her two kids who were sitting across the aisle. There is plenty of room, but as there is no seat divider, I was always a little uncomfortable, that I'd turn or roll in the wrong direction while sleeping and give this woman the wrong idea about my intentions.
One disadvantage of coach on long-distance trains with a full passenger load is that coach passengers are not assured of access to reservations in the diner. (This was back when the Silver Star had a diner.) Thus, my dinner that evening was a pizza and a bottle of wine in the cafe car.
When I got back to my seat for sleeping, the lights were turned down, and everybody was quiet. The Amfleet 2 coaches have curtains on the windows, so I had no problems with being disturbed by outside lights from passing towns, stations, car and truck headlights, etc. I brought along a nice stadium blanket that works fine, and I balled up my coat to act as a pillow. I was reasonably comfortable except that, for some reason the seat cushion felt that it was stuffed with concrete. (This sensation also happens to me on some day trips, too.) The worst thing was that I was reluctant to get up and use the restroom, as this would mean waking up my seatmate, who was sleeping very nicely. By the way, the restrooms were very well cleaned, and they even had a card on the door noting (with the attendant's signature) when the room was cleaned. Looks like they did it every couple of hours. This doesn't always happen.
I woke early in the morning, a little disheveled, but washed up, and then went to the diner (no reservations needed) for breakfast just a bit after we left Jacksonville. My seatmate and her kids got off at Orlando, and I had the seat pair to myself for the rest of the trip. Most passengers got off at Orlando, but a lot also got on, so I was happy I had the seat pair to myself. When we got to Tampa, the crowds at the station made it look like it was on the Northeast Corridor. I can see why Brightline/Virgin Trains thinks there's a market in this corridor.
On the trip back, I had a sleeper reservation. Would I do long-distance coach again? I'm not sure about a 24 hour trip to Florida, but I night think about it riding the Capitol Limited to Chicago. Generally, though, if I can afford a sleeper, I'll take it. My back isn't what it used to be, and those concrete seat cushions keep me up at night, especially if I can't get an aisle seat to allow frequent trips to the restroom.