We've taken the autotrain several times and for a few reasons. The first is that we like having a car at Disney World, it just makes it easier to park hop, go to non-Disney areas and come and go as we please without having to wait for crowded buses. Second, we don't like flying if we can avoid it and by the time you fly a family of 3-4 and rent a car, the autotrain is about the same if not cheaper. Third, we actually find the trip relaxing and kind of a transition to and from vacation. We take a computer and watch a movie or two to pass the time, catch up on reading or music . Fourth, packing is much easier..when in doubt, toss it in the trunk!
While we do prefer getting roomettes to have the beds, as long as the number of travelers is even, we don't mind being in coach. The challenge is when there are an odd number of travelers in your party and one of you is seated with a stranger. That can get kind of weird at times. Last year, there were 3 of us traveling. I had just gotten into my seat when an older woman came along who'd been assigned the other seat. She started questioning me about being in the wrong seat and when I assured her I was not, she was clearly not happy. My wife agree to switch with me and that worked out better but it was hard since the woman kept complaining. Amtrak used to leave the other seat open when there was an odd numbered party but that seemed to have stopped a couple of years ago. We've also thought about getting one roomette while the others get coach seating and take turns sharing the roomette for sleeping and relaxing. The problem would be meals for I don't think the person in the roomette could join the others.
All things considered, we like the autotrain...but the prices have gone up quite a bit in the past few years as more people seem to have discovered it.