Meh. It is rather slow-paced and talky, which isn't really the strongest way to end a season. Say what you want about RTD, his finales were never slow-paced and talky.
We start with a decentally done sequence of Clara in the Doctor's timestream. The splicing of JLC and footage of the various Doctors was rather clunky, but then that should have been expected given they were merging standard def with high def. And really, the only one that really looked bad was Troughton stomping by Clara. Although I wonder why they decided to splice footage with Hartnell in as opposed to having David Bradley fiml the scene. I think that would have worked out better, but maybe he was unavailable, off filming the docudrama.
Ironically, despite being their creator Moffat just doesn't write Vastra, Jenny and Strax as well as Mark Gatiss did a few weeks ago. Strax has some fine one-liners once again, although his cofusing genders is starting to reach a limit. I like the joke, and do smile every time he calls a woman "boy" or ironically this week he actually calls a boy "girl." But, this guy was a nurse, after all, and that's a job which kind of requires some knowledge of how to differentiate genders.
And what the hell is the deal with Strax in Scotland anyway? Does he go there on his weekends off and spar with that big muscular dude?
As predicted, we the audience don't learn the Doctor's name, though since Clara now remembers the events from Journey to the Centre of the TARDIS she should presumably now remember it. Or at the very least she'd remember River saying it to open the TARDIS door.
So this time River is the data ghost left behind in the Library's computer core. The line about being left behind like a used book is a nice touch implying she doesn't really enjoy spedning eternity in a virtual world looking after imaginary kids after all.
And finally, John Hurt. Obviously he is a past incarnation given the Eleventh Doctor talks about him in the past tense. Clearly, this incarnation didn't call himself the Doctor, which I guess is how they're going to get around him being a previous incarnation but not having to adjust the numbering so that Matt Smith is actually the Twelfth Doctor. I see some people suggesting he's from before the Doctor began using the Doctor name. and that could tie in perfectly with the Brain of Morbius and all those other faces which were supposedly other incarnations of the Doctor. However, the stuff about "breaking the promise" implies to me that he probably is later incarnation that chose for some reason (Time War, perhaps?) not to call himself the Doctor.