I have a theory...
Pretty much since the beginning of the series (or at least, since the Admiral Cain story arc), I've been wondering how much from the original series the writers would be borrowing and remixing into the new series. Particularly, I've been wondering about the War of the Gods arc from the classic series; it was a little wacky and supernatural, but at the same time kind of interesting. Not really the sort of thing that would transport well into the new series, though... or so I thought initially.
Starbuck is back. She was inexplicably transported to Earth, where she took pictures and gathered data, and just as inexplicably transported back to the fleet. She appears to have an intuitive knowledge of the location of Earth. All of her equipment, including her Viper, is brand-new and pristine. This reminds me vividly of the experiences of the Viper pilots in the original series who were taken by the "angels".
The Cylons have a God. Initially I was very uncertain as to where the writers were going with this idea, since the "one god" angle has strongly Judeo-Christian overtones, especially when used as a foil to a polytheistic culture. It seemed manifestly unlikely that the Cylons were going to be cast as the "good guys," which is what this association would imply to most people. Then it occurred to me: in the classic series, who was the voice of the Cylons' Imperious Leader? It was the "fallen angel" who found his way to the Galactica. What if the remixed version of this figure has set itself up as the Cylon God? Could this give us hints about the nature of Head-Six and Head-Baltar? It would certainly explain how Baltar's prayer that the child be cured was answered.
If my hypothesis is correct, that would imply that Starbuck is not, in fact, a Cylon. Baltar might be, but I'd lean towards not, if only because the "fallen angel" Cylon God seems so intent on corrupting him or otherwise deceiving him into his service/worship, which is something one does to humans. No guesses at this point as to who the last Cylon actually is, though... The only person we know for certain isn't is Helo, since he's the father of a half-Cylon baby with Athena.
Also, poor Anders.
So, what do you think?