We took a First Class train on that route last month during the day, so can't tell you anything about the sleeper accomodations. Train was average- not as nice as some where the seats are in glassed-in compartments, but clean and well-maintained. They checked our passports almost as soon as we pulled out of Budapest, so keep yours handy. You'll probably be awakened in the middle of the night as you go through Slovakia- our passports have an "SK" stamp even though we didn't get out of the train.