I guess I must have much lower standards for acting than most of my f-list, because I didn't mind the current Ruby actress' performance. It's not that I thought it was awesome acting, but it didn't think it was awful either.
Overall I enjoyed this episode a lot. Like everybody else I liked that Sam confronted Ruby about using women as hosts, and that she then used a braindead woman as a host instead.
I wasn't squicked over the necrophiliac associations of that. First, it was obviously not a true corpse, because the body was still working with the help of life support machines, and that just switched over to Ruby. Also, in fiction I'm not even all that squicked by actual necrophilia. Okay, so it is slightly gross if a character uses a lifeless dead body as masturbation aid, not to mention that it is disrespectful if the person that body used to be didn't consent to be used that way, kind of like disrespecting funeral wishes is wrong. More so in fictional universes that allow for the option of after-death awareness (that dead woman could be around as a ghost after all, on top of her traumatized relatives who may think she miraculously recovered and then vanished or just don't know anything), but well, viscerally I don't really care that much. And animated dead bodies are eroticized so often (cold, hard vampire bodies etc.) that I'm really used to that.
I didn't find it OOC that Sam slept with Ruby in his downward spiral after Dean's death. And Sam and Dean patching themselves and each other up stoically was great h/c-oriented fanservice.
One thing I wondered though was about their demon-stabbing knife. Is there some method to when it doesn't work that I missed or don't recall? The Crossroads Demon got stabbed in his hand and stayed in the body, and the other, more powerful one was even stabbed in the chest, but I guess that one was special somehow? Does the host need to be killed with it for the demon to go?