My only minor complaint about the 50th have to do with the fact [spoiler] Clara's in it. [/spoiler]
Other than that, wonderful in every way.
[spoiler]There were definitely good big chunks where she felt like a third wheel. I think it was wise not to give Tennant a companion and to work Piper in in another capacity instead; this really is a story about the Doctor and what he does when he's on his own.
But that's precisely why Clara IS important. The new series has been flogging the idea since Runaway Bride that the Doctor needs companions because they keep him in touch with his own humanity. They keep him from going overboard and doing crazy shit.
Like, y'know, genocide.
There was a minute there where it really did seem like Tennant and Smith were going to go along with it, agree that Hurt had no choice after all. But Clara points out that that's bullshit, and suddenly the spell is broken.
Because, really, the very idea of the Doctor wiping out his own people -- it's a fucking brilliant conceit, but it only works if it's a piece of exposition, if it's some other, intermediate Doctor who doesn't really count. If we don't actually watch it happen, with one of the Doctors we know and love pushing the Big Red Button.
Because he wouldn't do that. Not really. Not any of them. Wipe out the Daleks? Sure. Make the Daleks wipe themselves out? Even likelier. But the idea of one of the actual Eleven Doctors throwing the switch to blow up Gallifrey? Nah.
That's what separates Doctor Who from Torchwood: in Torchwood, no-win situations are mandatory, even ridiculously contrived. In Doctor Who, there's no such thing. There's always another way.
It's true that Eleven's run has been characterized by running from his own inevitable death -- but it's also been characterized by facing it and finding another way. Finding that there's no such thing as inevitability (unless you really need to write the Ponds out). And Tennant pretty much gave us the mandate for the Christmas Special: now he's going to find his way out of his death at Trenzalore.
The Moment calls him "the one who forgets" -- but now he's the one who remembers. He's the one who stops running. After spending his life running away from Gallifrey, now he's running towards it. He found another way -- because of course he did. Because that's what he does.
It just took a little push from one of those stupid apes he's so fond of.
Now, we clearly haven't seen the last of Grim, Angry Doctor -- Capaldi's scowling eyes made that clear. But there's been a change now. The Doctor's done the impossible once again, and now he's found a way out of his greatest regret.
That's #11's legacy. As surely as 9 and 10 are defined by the shadow of the Time War, 11 is the Doctor who got out from under it.
And left 12 with plenty on his to-do list.[/spoiler]