Spoilers - don't read if you haven't see it yet
I hope that was fair warning enough! If not, you've been warned...
Regardless of all the other issues with this film, how cool is it that he got away with murder? Basically he committed the perfect crime, which was likely made easier by a less than enthusiastic police investigation (until far too late to make a difference).
He got away with it, and now he'll have to live with it. Which, of course, was apparent in the final scenes. He didn't get away scott-free, because he has to live with the fact that he murdered two women.
But at least he avoided actual prison, though he'll be sentenced to the prison of his own conscience for the rest of his life. I got the impression that he wasn't a total sociopath, so he'll have to live with the regret.
See my IMDb listing here: http://www.imdb.com/name/nm2482070