Muss, my wife and I took Amtrak's Empire Builder from Chicago to Whitefish, MT for a trip to Glacier National Park last summer and then back again. It was a mostly marvelous travel experience. Bigwheelzip's description was spot-on, and I will just add:
The larger sleeper compartment with the toilet inside was way more money and, though a bit roomier, has the downside of the toilet being in there where you're sleeping. We had the smaller sleeper, with the pull-down bunk atop the facing seats that fold down into a bunk. It's cozy, and whoever gets to crawl into the top bunk had better be agile and, preferably, of smaller stature to make the move.
Mealtime was by reservation, three seatings if I recall, and surprisingly fun, as tables are for four, so you share with another couple for each meal. Folks who travel by train are in interesting breed, and we met some great people. Food was really good, and included in the price of our ticket, except for any alcohol.
There are toilets on both levels of each double-decker train car, plus showers on the lower. Again, cozy but comfortable.
Our return trip was, I think by default, in the same sleeper compartment, so we got to see what we had missed on the way out. A nice touch, I thought.
Only downside, and it was bearable but annoying, was a large family group traveling together in several compartments and including several teenage cousins, who seemed at every opportunity to ditch the grown-ups and gather in the sleepers next to ours to cut up and cuss. We could've ratted them out, but chose to just live and let live.
Have fun!