I actually think Jonatello is onto something. "It" would affirm Ben's statement in ROTJ of Vader being more machine than man. It could also help to explain why Obi Wan did not hesitate in confronting Vader on the Death Star; he thought there was no one left to save, just a sort of reanimated carcass. To the audience as well, Vader seems completely distant and the last of sympathy, the human connection, has left him.

Vader no longer recognizes his human nature and uses that quality to distance himself from moral judgment. He serves himself now and only later in ESB when Luke shows up, do his human qualities and his capacity for "human" moral judgment resurface. "It" may not be just Padme but his entire human nature.

In any case, maybe I am reading too much into it. The Cutter's work really is very good and uncovers much depth in the ROTS story I previously thought not possible.

EDIT: In response to Tobar's comment, Vader's unemotional and self-serving quality make him "evil." With no moral nature, he is unconnected with the force (life's representation) and what Obi-Wan would consider evil. Vader has changed into a machine which is driven only by the need to survive and better its own conditions; therefore, it cares for no one: evil.