This episode takes everything since the third season finale and brings it to a fever pitch, tossing out several assumptions about the direction of the story in the process. In other words, it is exactly what the doctor ordered for a season that has been uneven at best. The more serialized structure of the season has not always worked to the series' favor, but the fruits of such labor are indeed sweet.
I'm not sure if the season arc always included an early discovery of Earth, though it's certainly possible. There was a great deal of concern just before the writers' strike that the series would not return for the second half of the final season, and that this episode would be the end of the show. That makes me wonder if the arc was designed to bring the series to the doorstep of Earth, just in case the series came to an abrupt end (though some indications are that the final episode would have been the conclusion to the cliffhanger). After all, even if so many other mysteries remained unsolved, at least the journey could have ended just before that final scene, right?
Perhaps not. Because as celebratory as those first moments in Earth orbit were, the promise of 12 more episodes (thanks to a slight expansion to allow the finale to have necessary scope, ala "Lost") tells us that there's plenty of story left. And the final scene itself is a grim reminder of the "grass is always greener" principle. It fits the Galactica mythos rather well, for the ragtag fleet to find Earth, only to discover a nuclear wasteland instead of a homecoming.
Of course, it's not that simple. That nuclear wasteland was giving off a Colonial beacon signal, and that nuclear wasteland apparently saved Starbuck, gave her a shiny new Viper, and knew how to send the signal by interconnecting it to the Cylon activation signal for the Final Five. The weather nuclear remains of New York City (or possibly the Temple of Aurora?) are a great cliffhanger, but also seem a ruse. Had the alliance found Earth without help, the state of the planet might have been a crushing blow, but there's too much evidence that there's much more to it.
The process of getting to that moment of revelation was some of the best material of the season. The tension hit a fever pitch, and the writers managed to convey the sense of chaos throughout the standoff. Ironically, despite setting himself apart from Roslin on several occasions, Lee seemed to resort to her brand of tactics when dealing with D'Anna's gambit. It wasn't necessarily wrong, but it was a calculated attempt to demonstrate his strength. At the same time, I'm not convinced that Roslin would have avoided the agreement with the Cylon Rebels that came after Kara's moment of realization. And something tells me that alliance will be necessary, because the rest of the Cylons are still out there.
As everything seemed to smack heavily and messily into the fan over the course of the episode, the authentic character moments made it all work. Roslin seems committed to the path of truth, wherever it might lead, even when it means giving Baltar the chance to speak on their collective behalf. Adama's reaction to Tigh's confession was very well done. A number of character reactions to the unveiling of the four new Cylons were postponed by the jump to Earth, but they will most certainly be coming.
There are some serious issues to be resolved in the second half of the season. First and foremost, there is the revelation of the final Cylon, which should be interesting, to say the least. D'Anna specifically said that the final Cylon was not with the fleet at the top of the episode, and at that point, a number of very important characters (notably Adama, Roslin, and Baltar) were all on the basestar. It plays into the notion (at this point, very well supported) that Baltar is the final Cylon. But I still think it would be too obvious to take that direction. Wouldn't it be a huge moment to discover that Leoben was right all the way back in the first season, and Adama really has been a Cylon? It would play into the theory that both Humans and Cylons were meant to come to this mutual moment of transition.
The arrival on Earth will eventually tie into Kara's visions and her resurrection, just as this mysterious signal from the ruins of Earth is connected to everything that has happened since the beginning of the series. I'm left with the notion that the signal is not, in fact, a Colonial signal per se, just as the activation of the Final Five was not typical. The signal may tailor itself to certain individuals in a certain way, with the signal intensifying at the various markers along the path. For some, it may be visions. To others, it may be music. To Kara's special viper, it may be a Colonial beacon. And it could be something automatic, something meant to draw the rest of Humanity and its children to the memory of Earth. (In fact, it's possible that the idea is for both Humans and Cylons to see the ruins of Earth and choose a different path, ala "Babylon 5".)
There's also two other small matters. Roslin wasn't supposed to live long enough to get the fleet to Earth, and there's no other leader who died along the way who would fit the profile. So is it possible that the Earth that was found is not, in fact, Earth? From the visible land masses, it's hard to say for sure. But after tossing that prophecy out so many times, the writers will need to close that loop. There's also the continuing threat from the rest of the Cylon fleet. It's hard to imagine that those models would just choose to live and let live.
The bottom line is that there's plenty of story still left to be told; the only question is when the Sci-Fi Channel will allow it to air. Current estimates give the beginning of the final 12 episodes around the first quarter of 2009, which probably means March 2009, given how the network parses words. In effect, it's the same wait that "Lost" fans are currently enduring, and far less annoying than the long hiatus of shows like "24". We can blame the writers' strike, but this is all about the network and their need to string out their one non-reality critical hit as long as possible.
In the meantime, there will be "Caprica" and perhaps another "Battlestar Galactica" TV-movie, similar to "Razor" last November. It will be a long wait, but at this point, I'm happy just to know that the series will come to a definitive and creator-driven end. Much like "Lost", the establishment of an endgame scenario long before the writing of the finale is just what the doctor ordered.