We traveled on 1st class lower berths of SE19.
It is quite easy to find the correct trackway as the train number and trackway number is shown on different displays in the waiting room and on tracks in Hanoi.
A ticket inspector was waiting at each wagon at the door and the wagon number is clearly indicated on each one. Anyway the inspectors were very kind and checked our printed e-tickets before we get in, so don't be afraid to take the wrong train.
Our train left Hanoi right on time and arrived in Hue at the expected time also. If you starting your journey from a terminus, I think arriving 30-45 min before departure time should be enough.
The train in itself has a quite charming old fashioned style.
Pillows and blankets were nice and clean. We used silk sleeping bags that we bought in Hanoi for that occasion anyway, but it is probably not mandatory.
Cabin was also clean (didn't see any insects) and the door had a lock usable only from inside. The cabin was equipped with two 220V power plugs and a dustbin. There is two roof lights and each berth has a light for reading. There is room for aprox. 30cm tick luggage under the lower berths.
The air conditioning was quite noisy and expect to be maybe a bit cold if you are not under the blanket or wearing a pullover on the upper sleeper as the air is coming from the roof. Of course, you can't shut it off or set the temperature.
We brung some snacks and beverage so we didn't tested the food in the train, nor the dining wagon.
A singing guy passes through the wagons with food and drinks from time to time, so you can purchase food without the need to leave your luggage unattended if you are tavelling alone.
Although, it only travel at 75km/h at top speed the train is quite noisy and bumpy. But, if you are a bit tired you will for sure sleep a few hours at least. Bringing ear plugs is always a good idea, though.
Your sleep quality will depend mostly on your neighbors and their will to sleep. Ours were also tired so, no problem hear.
Toilet were clean at departure, but as the train is bumpy, it's not always easy to aim right for men.
Therefore, it was stinky and wet after a few hours. It appears to have not been cleaned during our 14 hours journey. Bring toilet paper.
The wagons are also equpped with a free water dispenser and a sink where you can brush your teeth or shave (If you like challenges).
Overall, it's a very pleasant journey where you can see beautiful landscapes and have a general taste of Vietnam.
You also don't loose your precious day time taking a plane and spare the money of the accommodation for that night. I would for sure recommend that adventure.