Many times.
Most recent - an overnight on one of the "Green" trains (the slow, traditional kind) in China - a small berthing compartment - me and 5 other people. Very basic but the adventure more than made up for the surroundings...besides - I was asleep most of the time.
Most luxurious - riding the Ghan from Adelaide to Alice Springs in Australia. I splurged and had my own private room. Nothing like waking up in the morning, getting dressed, going to the dining car, sitting down at table and, as the sun rose, watch a couple of kangaroos race along side the train.
Curiously different - Checking into a single sleeping car on a siding at Exeter-St. David in the evening - going to sleep in my berthing compartment and the next thing I know - a quick knock on the door, the car steward entering with tea and crumpets, a quick nod from him, and "London in 20 minutes, sir." They attached that car to the train sometime during the night and I never felt or heard a thing.
Childhood memory - taking the UP from Sacramento, California to Council Bluffs, Iowa all by myself for a summer visit with my Grandmother. Sleeping in coach, feeling a gentle tap on my shoulder, waking and seeing the Pullman porter from the next car signaling quiet and gesturing that I follow. Getting to the vestibule between cars where the porter opened the top half of the door and feeling, smelling the salt air of the Great Salt Lake. Looking out across the moonlit water and finally having the porter tell me this is his favorite part of the trip. Nothing more was said. When we came to the end of the bypass, he closed the top door, indicated I better get back to my seat, and he, in turn, went back to his Pullman.
