I thought an interesting interpretation of the film would also be to see it as a depiction of the process of emancipation by Sutherland's wife. At the end she's smiling, because she has come to be freer. Her husband couldn't deal with the "supernatural", couldn't accept some facts of life, so in the end she was the stronger person, because she could.
Anyway, I really like the film. Last time I saw it, I rated it a high 7/10.