This is the second Christmas special to serve as a last hurrah for a Doctor and a much better one and The End of Time! For one thing, I was still enjoying Matt Smith's time as the Eleventh Doctor and for another it drew in so many of the elements from his and earlier eras. The crack in reality, the Angels, the new Cybermen, the Silents and more.
The Christmas aspect is... Minimal at best. Enough to make it fit, but this episode would have been fine without it.
There is a lot going on, as dangling plot threads are tied up, matters of regenerations and lost Gallifrey are dealt with and more besides. Smith seems to really be invested in making his last appearance count and does a spectacular job as the aging and then dying Doctor. No whiny, angsty, twenty minute send off for Eleven!
While not every idea hits fully home and a few questions from Smith's era are left unanswered, this is a good send-off. It still fits the fairy tale style of storytelling that will forever be a stamp on the Eleventh Doctor's run, but is more coherent than many of his stories and has some real emotional weight to it too.
Next comes the new, current and best Doctor of the modern show and a really cool first Christmas special for him too.