I have to admit, after the initial prologue, I thought the movie was losing its edge. It is very subtle most of the time and it might alienate those viewers who think it would be even darker. But if you stay with it, all the planting will be ripe for seeding. And you will enjoy the really crazy humor this movie has to offer. Largely in French, Saul Rubinek is thrown in as an American to mix things up.
I guess if you can criticize one thing above all others, it is the fact, that the characters might have needed a bit more exploration. So you could feel more for them. On the other hand, it might help you enjoy the movie more (especially if you're not sure what to think of the doctor, because you can read ambiguity in his motivations). If you're not afraid go ahead and try this out (the fact it's black/white shouldn't bother you either)
