After tonight's Battlestar Galactica, my friend Jason and I were beginning to lose heart a bit with the Baltar/Number Six storyline. It seemed that in their eagerness to create the "Baltar is a cylon" red herring, the writers were going to sacrifice continuity. Or, worse, they would make the "Baltar is a cylon" not a red herring at all, and pitch continuity out the window altogether.
Then, finally, we got it. Baltar is not (merely?) mad, and Number Six is not a chip in his head. Number Six is not a cylon at all.
OK, before I lose you, consider this: the Number Six in Baltar's head (we'll call that one "Baltar Six") seems to have the ability to tell the future. Not only do no other cylons seem to have this ability ... we've never even seen the other Number Six models have this ability.
"Our baby will be born in this room" is not secret cylon knowledge -- it's a prophecy. Even if Baltar Six were a cylon, how could she know that? She could not know that Boomer would survive on Kobol, and she could not know that the humans would not assassinate her/blow her out of the airlock, and she could not know in which cell in the brig they would detain her.
These last two episodes (linked by the apparently unnecessary "To Be Continued") were a major shift in the storyline. Besides Roslin, the only major religious figure has been killed. The relationship between Adama and Roslin has strengthened to the point that their tensions can no longer be the impetus for the human side of the story.
Instead, we have dueling prophets. When Roslin has visions, they come off as drug induced hallucinations. This does not mean that they are not drug induced, but by the same token it does not mean that the visions aren't real.
Baltar Six is the manifestation of Baltar's prophecies. She may be, as she claims, an "angel," though given her past behavior, "demon" might be a more specific appelation. Just as likely, he may be mad, and his hallucinations of her may be the only way he can understand his own prophecies.
At this point, I suspect Giaus Baltar is a prophet -- either a prophet of evil, or a prophet of the cylon god. Baltar Six's only connection to all the other Number Sixes is that she looks the same in his head. All the other Number Sixes are cylons, but Baltar Six is not. If this is the case, it is really a clever bit of writing, because it sucks the audience into Baltar's point of view, and causes us to be taken in by appearances (much like Shakespeare does to the audience in Othello by having it open with a half-overheard conversation).
Of course, I reserve the right to change my mind without notice.