Re: Spoiler whore's thread! (enter at your own risk)
You know the thought just occurred to me that the Final Cylon probably isn't from the Earth we saw in the last episode. Rather it's from "Earth 2." That would explain why the Four heard the music but the Fifth didn't. It would also explain the comments that the reveal will set the direction for the rest of the season. It's the key to finding "Earth2."
I kind of always thought that the "final five" were some sort of reincarnating cylons who could pass their consciousness down from one generation to the next. This would explain how they predate the original seven, but are still possessed with a history young enough to have "always" been human.
"A bend in the road is not the end of the road unless you fail to make the turn."