I'm just really impressed with the development of the characters. Each one of them have taken turns towards something else, almost opposite of what they once were.
Baltar is interesting, he's finally stopped caring what happens to himself. He's willing to die, and now has had his incredible burden lifted from his chest. But now is basically stuck in his position with the zealots, as he would no doubt be killed out in the fleet alone.
Tigh is another one, he's hated the Cylons for so long... And killed his Wife for collaborating. Now he will probably start hating himself, and terrified of what he might do.
I'm thinking that the last Cylon will be a shocker. I don't think it is Starbuck or Baltar, that would be too easy. But I still think that both of their characters are vitally important in the story as a whole. She is probably connected to the Colonists "Gods" in some way. An angel of sorts.
Baltar, I'm not sure. There was something that the President said about 5 priests and "He who shall not be named" in the scriptures. Which would be the final 5 Cylons and someone else, an orchestrator of sorts. I think Baltar is connected there, somehow. It would explain why he sees Six and seems to know things that he really shouldn't. And why she sees him. Possibly programming that is supposed to lead them both towards the finale. "All of this has happened before, and will happen again", fits together.
At least in my crazy a$$ mind.