Featuring the return of Stephen Moffat as a scriptwriter for DW, and okay, as Christmas specials go. (My own take on the various Christmas specials from various New Who eras: I love only two - The Runaway Bride and The Husbands of River Song respectively, i.e one RTD and one Moffat effort, but like most of them (in varying degrees). I think there are only two or three I don't like. This won't be one of them, but neither will it be a beloved favourite I rewatch, I think.
Structurally, despite being so Moffatian, it was weird, in that Nicola Coughlan who played the supposed Companion-character for the Special hardly shared any scenes with him and otherwise wasn't as present as you'd espect the Companion character to be, either - what scenes she had, she played well, but I couldn't help but think of how good she'd been as Claire in Derry Girls and wish for a DW/Derry Girls Crossover Christmas Special instead. Otoh, the Doctor did have quality bonding time with the special's other female character, Anita, who was lovely, but their relationship felt like a self-contained short story within the special, not really connected to the main plot.
The Doctor getting on his inner Seven in the scene where he deliberately insults and hurts Joy to make her angry so she breaks the mental hold of the Villengard engineered device was a rare moment for this particular incarnation of the Doctor in that it showed he, too, can be (emotionally) ruthless if he must, but of course the big difference to the Seven and Ace scene in Curse of Fenric is that the audience at that point was very invested in the Doctor and Ace relationship and knew Ace and her issues and her everythign really well, whereas this was only the second real scene of Joy and the Doctor, and we didn't have the chance to get invested into either Joy or their relationship. Nicola Coughlan radiated endearingness, so it still worked, but that's where the structural problem for me came in - this scene would have landed so much harder if the Doctor and Joy had shared scenes and bonded before.
(Mind you, as mentioned I did enjoy the whole Doctor and Anita sequence - and btw, now he's worked as her Girl Friday/household help for an entire year, we have new crossover and encounter possibilities - but still: in the interest of the overall story, I think the Doctor should have shared that bonding time with Joy, not Anita.)
The first year of Covid backstory for Joy (and her mother) and the direct hit at Boris Johnson and his government and their callousness indicates an ongoing rage of Mr. Moffat's I can totally get behind.
Not sure about the last scene. (And I happen to be a Christian.) (It's just - there are some things I don't want DW to depict.)