It sounds like a romantic way to cross the vast open spaces of Russia, leaving Moscow one evening and awaking to the Romanov's splendid Baroque capital. However the beds are cramped and uncomfortable, the train rattles far too much to get much sleep, and the toilets are disgusting. There was a certain charm to watching snow-covered fields and forests pass by in the half-light, but I suspect the view (particularly of a vast lake at one point) would have been all the more stunning during the day, and I wouldn't have felt like a zombie the day after.
Leningradsky Station, Moscow
Updates
Is this your business?
Take ear plugs if you're likely to be bothered but the gentle rocking as the train trundles along is hypnotic