The flashback blonde Ruby was an amazingly close reproduction of season 3 Ruby, which either means both bodies resemble the original witch Ruby, or that Ruby has a type. Either way Our Lady of the Sulfuric Smoke went to a fair amount of trouble to find a host body capable of blonde hotass smirking in the style to which she'd become accustomed. Jane Doe, on the other hand (so convenient to have no grieving relatives), was a forced choice, and that sweet, serious, round little face was not made for smirking. Research has shown that if you force your face to smile, you will actually start feeling happier. So if Ruby's new face is naturally sincere and serious, does that explain the diminishment of Ruby attitude and smirkitude? It does seem as if new!Ruby is rather in love with Sam, and that could also be a reaction to really living in a human body (it's breathing, circulating blood, digesting food, healing, so I consider Ruby's body to be alive). She's kind of a Pinocchio, the demon girl who came to life, emotional life, sexual life, the whole shebang.
Castiel (sigh) is as incomprehensible to humans as they are to him because they are focusing on two completely different planes of existence. To Sam and Dean, human existence is a high priority, but to Castiel of the infinite gaze and lifespan, it's not that big a deal if a human soul has its time as an embodied physical being cut short. That soul will (presumably) be going on to bigger and better things, for a much longer period of time. I can see Dean being disillusioned and upset that Castiel would seem to value human life so lightly, but I hope he figures out, or more likely someone explains to him, that Castiel just has a different perspective. Because Castiel and Dean should be BFFs forever and ever, amen.