Pretty unnecessary and I find it really hard to get properly engaged in the main story, it's really slow and uninvolving. I also kinda disagree with the decision to return the Doctor's memories of Clara.

However, it might all be worth just for the Christmas Truce scenes, because they're genuinely beautiful and never fail to make you emotional. Maybe that should've just been the entire episode.

Alas! It's a good regeneration scene, give it that. Hello Jodie Whittaker!