I traveled from NY to LA via train with one planned stop-over. We had coach seats which were a little less expensive than air travel, so it's not really worth doing unless you're in it for the experience of it.
It was an enjoyable experience tough, and we'd probably do it again on another route. While it would have been nicer to have a sleeper, the coach seats were pretty comfortable.
As someone who's done lots of long-haul (Texas–Chicago and Texas–Maryland) rides, one (or a few) long-distance coach trip is perfectly doable, and even enjoyable if you like train rides; but I feel that it gets unbearable pretty quickly as a regular occurrence. Also a big factor: travelling with an intimate (someone you can literally lean on) makes sleeping much easier, even in coach.
Not in the US! I would love to travel by train whenever time permitted, but it is prohibitively expensive to travel by sleeper car.