OK, I love Paul Giamatti, so of course I had to watch it, and as per usual, his performance is top notch. The story is interesting, yet flawed, but I rarely laugh as much during a film as I did during Cold Souls. Because of this I can forgive the premise of souls being taken from the body as the extracted goes about relatively normal, albeit a bit "lighter," as Giamatti states. The soul, in most definitions, is the person himself / herself. It is one's personality, character, emotions, talents, gifts, etc. So if that is removed, well, according to most definitions, you end up with a sack of flesh.
Overall I enjoyed the film considerably, even though the ending was somewhat wanting. Regardless, certainly worth the watch.