As has been painfully noted already, it was great until the rewrite. One of the best Christmas eps, imo. I can think of worse things than another season of Clara. I was digging their relationship in S8. I'm sure I will in S9. Two things:
1) Taking her change of mind as a given - I wonder if there was ANY way to rewrite her in without it being so clunky? Take out the old age scene altogether?
2) As if we need more proof of the rewrite, in the first scene before anyone talks as the camera pans up the stairs - there's a chair lift. Had the show gone on as planned that would have been a really perfect clue. We'd all be applauding it. Now, utterly useless. Moffat will make a statement in a couple weeks that she's renting the flat from her Great Aunt who recently moved to a nursing home.
Anyway, I still loved it. Shona was fantastic.
Oh, one more thing - since we know Santa is a product of the dreams then in the last scene of Death in Heaven, the Doctor has already been taken over by the crab.
I mean, I wouldn't put it past Moffat to hand-waive Danny's death away via the headcrab, especially since the tangerine appears at the end of the whole thing as the Doctor gets into the TARDIS with younger Clara.
There was much to love about the episode, and much that -- had it retained its artistic integrity -- would've worked to dispel many of my criticisms of Moffat's approach to running the show. But no, he pretty much took all of that and Moffated all over it.
Can they make Clara work next season? Yeah, probably. My guess is that this will be accomplished largely by treating the events of last season as not mattering. That's another gripe I have with Moffat's style -- his seasons seem to generally be self-contained to the point where they almost bear no connection to previous seasons. Hey, remember when Rory was an Auton? No? Probably that's because it was used as a quick device to just bring him back to the show, and then was quickly ignored/forgotten/hand-waived away when they wanted Amy to be pregnant. And then life went on as if it had literally never happened.
When you engage in season-long arcs, they stop having any real meaning or impact when you just as quickly ignore them when you move forward. Say what you will about Joss Whedon's style, but at least when he kills someone, either (A) they stay dead and you see the impact of that resonate throughout the rest of the show, or (B) they come back, and you see the impact of THAT resonate throughout the show. With Moffat, it's more like "Huh? they were dead? Ok. Well....now they aren't. Happy Christmas!" or "Right, right, right, they're dead, but so what? Time to move on, back to normal." I mean, chrissakes, even ****ing ADRIC'S death had more meaning than half the reality-shattering super-important moments that Moffat seems to introduce, build towards, execute, and then disregard.
And I say all of this as someone who LIKED this past season for the most part, who was ABLE to accept some of the more bonkers and stupid things like moon dragons laying eggs the size of the dragon mere seconds after hatching from the moon, or whole forests appearing overnight and then apparently all of humanity just "forgetting" that it ever happened because um....they "wanted" to forget. Or something. Whatever. Pay no attention to the Moffat behind the curtain. I could actually ACCEPT all of that stuff and take it in stride, because the emotional journey that Clara and the Doctor seemed to be on was one that felt real. Clara's journeys took a toll on her and her relationship with Danny. Clara's addiction to excitement with the Doctor came at a price. The Doctor's prickliness necessitated that he have someone like Clara and he recognized it, even as he watched it damage her. When Danny died, it really seemed like both Clara and the Doctor felt the death, and it had real meaning. And with the Christmas special, we got a few more minutes with them all to say more meaningful farewells, and to show that Clara's life had been real, meaningful, and yet tinged with regret and pain...all because she accepted an invitation from a floppy-haired 1000-year-old man to travel all of space and time with him in his funny blue box.
And then Jenna Coleman wanted another season so they gutted all of the emotional impact of that. All, apparently, at the cost of also introducing a character who seemed quite interesting, and a welcome change from what we'd seen up until them. A plain, ordinary shopgirl, rather than some "Impossible Girl." A girl who was bored with her life, who also apparently carried her own regrets, and who had a penchant for sci-fi movies. I was really looking forward to Shona joining the Doctor. I think she'd have made a nice change of pace in a companion. Maybe she'd end up annoying, but I saw glimmers of really interesting stuff in her performance. And now? Well, now she'll probably just be an afterthought.