I’m kind of mixed about the episode and the way Matt Smith was sent off and Capaldi’s doctor introduced.

First off, the good:

Matt Smith put up what is the equivalent of an Emmy winning performance, capturing the angst of aging and shifting the perspective of the Time Lord who doesn’t age to one who ages immensely while those around them change not at all

This was one of the better acted episodes in recent years all the way around.

Putting the Doctor in defense of Christmas (on Trenzalore no less) was interesting, and explains why the planet is so important.

Interesting way of wrapping up the loose ends of why the crack in time exists, including that the Doctor isn’t infalliable.

The Silence must fall is given new meaning, but not sure I like the way they tried to resolve it - the Kovarians were a splinter cell

The bad:
Rewriting canon about the Time War, regenerations, and what happens to all that which has passed in time over the past several seasons. This is a problem that began with The Moment.

Bringing back Amy Pond was a bit of mirroring with the introduction of Matt Smith as the Doctor, but it didn’t quite feel right. Amy got a proper sendoff previously. There wasn’t a need to bring her back, although they both got to quip about the haircuts/wigs (breaking the 4th wall).

The deux ex machina of giving the Doctor new regeneration(s) gets around a thorny issue as to just when and how the Doctor will end. There’s a certain amount of pressure and gravitas that comes with knowing that you’re going to come to an end. To set affairs right and to do right by those around you. That was one of the motivations for The Doctor defending Trenzalore.

Now? Not so much, though there’s perhaps a need to justify the extension.

I think that the physical regeneration gave short shrift to Capaldi’s entrance. One moment, it’s Smith. The next, it’s Capaldi. It remains to be seen how he’s going to fill Smith’s shoes. Well, I hope.