Tanis said:
@BehattedWanderer: I think the Zylons were there to explain why Queen E1 was pissed at the 10th Doctor (remember the Shakespeare episode), as a plot device, and to show that the human race isn't completely screwed without The Doctor.
-Though, pretty close.
The main purposes of the Zygons were to introduce the "frozen in time" plot device so it wouldn't be pure deux-ex-machina/would make sense in the context of the show when it was used on Gallifrey (in the same way the scene with the sonic was used to hint toward the same "time to think about how to solve the problem" thing Moffat used back in Forest of the Dead), and to show how the Doctor's personality had been affected by the Time War - how he desperately needed to save everyone, to make up for when he (seemingly) couldn't save anyone. It was an episode about the Time War (the event that had defined the series since its reboot), but for me at least, the Zygons worked well as a more conventional enemy that lead up to the Moment when everything changed. Which makes sense, seeing as it was the Moment that put the War Doctor into that particular sequence of events to help him figure out what he had to do.
Honestly, my only issue with the Zygon plotline (aside from Ten consistently failing to identify them correctly, which just got annoying after a while) was the fact that if there were Zygons on Earth in 1592, why did the Zygons that first showed up on the show act independently of/not know about them? Haven't actually seen Terror of the Zygons, but that seems like a relevant point.
- - -
As for the resolution of the Time War itself, I believe that at some point in there it was mentioned that both the Time Lords and Daleks had been severely depleted by the war, and the Daleks were throwing "everything they've got" at Gallifrey. So I'm willing to believe that that covers the absence of the previously-named atrocities (the Nightmare Child and all that), because they'd already been used up (which left the end of the war 'standard' enough to not go into absurd special effects), and I'm willing to believe that while the Dalek race as a whole was not wiped out, any still fighting in the war were, with the freezing/vanishing of Gallifrey somehow setting off an explosion that destroyed the fleet surrounding because
science. That also explains why the Daleks that weren't around for the end of the war survived past the Time War into the new show, and it could also open up the option for any Time Lords that wouldn't have fought in the war and stayed away from Gallifrey (the Monk, the Rani) to have survived past it as well, like the Master did.
...and as for the fact that it negated something that defined the show for the last 9 years, well, maybe that's why the saving of Gallifrey is for the best: the Time War defined New Who a bit
too much at times, and being absolved of the genocide of his race gives the Doctor the opportunity to take a new path, play a new role, etc. It doesn't absolve his guilt entirely - he still
would have pressed that button if the other option wasn't available, so even knowing that he didn't, he has to live with the fact that he was
willing to do it - but it doesn't have to consume him anymore, the way it did (in different ways) for 9, 10, and 11. The Time War was a huge part of the mythology of the show, but if it was to keep growing, it had to move on. From a strictly objective/production point of view, the Time War came into play so that new viewers of the show wouldn't be overwhelmed with too much lore at once and be too confused to keep watching (which was part of why the FOX movie flopped), but now it's been long enough that the new fans have a decent enough understanding of the lore for the Time Lords to be properly brought back into the fold, providing a whole new set of circumstances to prevent the show from growing stale. For instance, now future Doctors will have to deal with the issue of what's to be done about the Time Lords - and what they were willing to do - when Gallifrey is found and brought back. There are whole new wrinkles to deal with.
(Apologies for the fifteen different points, I've just had a bunch of different thoughts about the impact of the episode since I saw it, and haven't really had anywhere to talk about it, so it all kind of came out at once here.)