Usually, prequels and pre-transmission minisodes are rather inconsequential little things. Not so The Night of the Doctor. Six and a bit minutes of incredibly significant material. The return of Paul McGann at long, long last - only to meet his fate. We hoped he would be in the Special, and the idea that he might be seen regenerating into the Hurt Doctor was high on our wishlist. And here it happens. It all takes place on Karn (last seen on TV in The Brain of Morbius) and the Sisterhood are present with their Elixir of Life. Leader Ohila has a range of flavours to choose from - fat, thin, young, old. Who'd have thought it? Eight chooses "Warrior" flavour (tutti-frutti obviously not being much in demand during the Last Great Time War).
For BF fans, the companions are mentioned. (And if you're not a BF fan, he might well be referring to unseen travels with Charlie Chaplin and Molly Sugden perhaps).
We learn that the Eighth Doctor has been avoiding the Time War rather than fighting in it. Events here force him to take part. The War Doctor is not born as a grizzled old man. Rather, it appears that the Hurt Doctor goes on to live a long and eventful life in the War.
If there is one slight misgiving about this, it does mean that future writers of books and audios are denied an epic finale for the Eighth Doctor. They can't have him fight to the death in the Time War (or anywhere else). He meets his end on Karn...