It was a great experience. I think generally they are not crime thingies. The only things that would put me off as that the cabins are very cramped (certainly the ones for two people- and manouvering yourself into the top bunk isn't easy). I'm not sure whether they have cabins for one- maybe they are a lot more expensive. There was very little room to get changed- if two of you are in the cabin you need to take turns. Finally, as there only washing facilities was a sink, you do feel after a couple of days that you could do with a shower- especially if you have stopped off somewhere and walked around in the heat. Byt overall teh views were wonderful, especially Switzerland, and the food was good. You will share tables with strangers at meal times (though breakfast can be in your cabin) but everyone was pretty friendly (although you will find many will want to tell you about their last half dozen holidays this year travelling across Canada/Vietnam/Australia...).
I liked sleeping on the train while it was moving but every time it stopped during the night I woke up.
Presumably your journey will be broken into steps as the real Orient Express will start in North France.