Cillian Murphy is really good in this. I actually can almost not think of another actor playing this particular role. It is very demanding and he goes places that I'm sure some people wouldn't dare go (or follow him for that reason). It really is a good movie. A weird little story with great actors all over the place.
I especially loved the ending, though they seemed to be unsure of how to go, since there are alternate endings on the disc. Very slow and very uncomfortable to watch, it is something that I hope will be cherished by quite a few people. Even if it only gets a home entertainment release (like in Germany) and does not see the light of the cinemas. I dare you to watch it