WARNING: BATTLESTAR GALACTICA SPOILERS!!!
I've been thinking quite a bit about your deus ex machina criticism of the conclusion of Battlestar Galactica, but – if you're interested and willing to hear me out and consider my reasoning – I think I've finally decided that that isn't quite fair.
If anything was deus ex machina, it seemed to me, it was the all-too-quick-and-easy decision by the whole society to "go native" on New Earth and to assimilate among the native humans. That pushed the bounds of my credulity moreso than did the idea of an FTL Drive, although I recognize the concessions one makes to the time limits of episodic television. Most of us, with our merely 21st-century technology, couldn't survive a jump back to such primitivism. And I certainly like my indoor plumbing too much to try. But the divine aspects of the ending to Battlestar? Not so problematic.
A real deus ex machina ending truly makes the ending thus-and-so. This perfectly lines up with Greek ideas about fate, which one can see in both their mythology and drama as well as in their more secular historiography. Whether explicitly or implicitly, it was characteristic of Greek views of reality that one had a pretty set destiny.
What we saw in Battlestar Galactica was, as should be no surprise, inevitably influenced by the historical infusion of Judeo-Christian perspectives into Western culture. Most important for the theology of Galactica is the higher vision of human freedom that came along with Jewish-Christian theology and anthropology, tempering the Greek determinism of a world where our destiny was either in the hands of the gods, particularly the Fates, or in demythologized belief in hard-and-fast fate.
So what we see instead of deus ex machina in Battlestar is actually much more akin to the Jewish-Christian idea of grace. God enters into the historical process in a way that offers a kind of aid but which still respects human freedom, as that, too, is the will of God. Battlestar incorporates this vision of things, featuring a number of "interventions" in history of the more dramatic sort characteristic of the Abrahamic faiths: inspired texts, mystical experience, encounter with other orders of beings.
But none of this adds up to swinging God out over the stage on the machine to decree the ending. Each of the characters has to actively participate in their freedom: doubting their own sanity, risking the Battlestar equivalent of the very post-Enlightenment ridicule of those who deny any veracity to religious experience or history whatsoever, and even risking their very lives. On what? On such moments of trust or faith in their intuitions of the meaning of their accumulated personal and shared experience.
Kara's final decision to start inputing musical notes from this experience she had been having – in light of her accumulated experiences? Chancey. Free. Out-of-her-fraking-mind insane. Very Kara. But not determined. Not forced upon her. Not deus ex machina. Instead, it was part-and-parcel of a grace-style theology that we had seen throughout the series. Now, certainly we can take issue with that if we want to, but if I'm reading all this correctly, I don't think it's quite fair to the writers to say that they trotted out a shockingly-deficient deus ex machina ending. It seemed perfectly consistent with the whole.
(And, should you have made it this far – since normally I wouldn't think of distracting you from your work by chattering away on your LiveJournal – let me just mention what a great deal of pleasure you have given me in A Song of Ice and Fire, and to thank you for it.)