(SPOILER)Things I felt didn't work well were the sudden disappearance of the Weeping Angels (I honestly missed the explanation of why they left, although I have been assured it was in the episode) and the Silence's sudden heel face turn, which was explained in the story but wasn't really given enough time to have an impact.

It's also not clear how the Doctor being given a new regeneration cycle ties in with his "death" on Trenzalore or if this is why Clara and the Great Intelligence could enter his timestream there, but maybe supplemental materials will expand on it.

As for the new regeneration cycle thing feeling cheap, though, the possibility of a regeneration cycle has been present in the series ever since the regeneration limit was first introduced (indeed, it's arguably the whole reason the regeneration limit was introduced in the first place), so the possibility has been there ever since the regeneration limit was a thing.