I can only speak for sleeper trains in general, but it's really a personal thing. Some (like me) find the gentle rocking of a railway carriage very conducive to sleep. Others say that the only way to sleep on a train is to have spent the previous night on a train...

I think it depends on how well you sleep in general. If you think noise, movement and limited space will keep you awake, you're probably right. If you're someone who relaxes on trains and dozes off easily, it can be a great experience.