I've only taken one trip on Amtrak, from Dallas to Little Rock. The best part is that it's a 'smooth' ride with a gentle rocking motion. But that, plus that the seats are large and comfortable compared to an airplane or a bus, is about all the attraction, for me. For some reason I had thought that a train trip would go through a lot of good scenery, but that wasn't the case. When going through towns and cities, it's about the worst parts you see-- presumably because railroads are 'old' now, so they pass through the old parts. And when going through the country, it's no different from going by car on the highways.
The timing/scheduling is bad. My train was over an hour late (by the printed schedule), but more seasoned passengers waiting knew all about that while I didn't-- you should assume it will be well late. And a major reason, of course, is that Amtrak trains must yield to freight trains on the main line, and thus they often have to go on a spur to wait for the freight to pass. This is because when Amtrak was first created, by the railroads giving up their passenger cars and assets to form it in 1971 (passenger service had become a money-loser for Union Pacific, Santa Fe, et al), part of the agreement was that freight trains would have the right-of-way in cases where one train had to go on a spur and yield. But even with all the should-be-expected delays, the longest one on my trip was after 10 p.m., some kind of mechanical problem; there was some announcement, but I don't recall if they mentioned just what it was. Anyways, we sat there immobile for an hour and a half. I had already been to the dining car (you are assigned a time), or that long wait would have been better. So, by schedule the train was due in Little Rock (I think) about 10:30 p.m., and it was about 1 a.m. when I arrived. The trip back was in daylight hours and without incident compared to the first leg-- just the usual hour or so late by schedule.
To sum it up... Amtrak takes as long or longer than a bus, and costs as much or more than an airplane. A comfortable seat and a comforting ride, by comparison, just doesn't make up for the time and cost, if those are important to you. But, it is worth experiencing, and if time and money are not such a factor, it should be a good "adventure."