This is not the intelligent horror movie the director wants you to think it is. There isn't a single scarey moment in it. It is gross and it is intense. It is also brutally realistic pointless gore with a very lame plot. The actors all do a decent job considering the lame material they have to work with. The Bulgarian actors are especially good.
The story of all this torture being for medical purposes is extremely thin and makes no sense when you think about it. Do people de penile transplants? Do people recover from eye transplants in a matter of hours? Do you really harvest organs with a circular saw in a filthy non-sterile environment? Heck, do you perform any sophisticated medical procedure on a moving train? Don't think so. So, once you come to that conclusion, the story is just idiotic with some great make up. The train can be a great vehicle for a horror movie, but this totally misses the opportunity to be an intelligent, interesting horror movie.