I liked this ep better than most this season, though it was a bit pedantic. It did at least have a proper 'story-shape' to it. There was some silliness (the zombie monsters in particular) but it held together mostly.
The most important scene in the whole thing is the one in the TARDIS's "replicator" room. For that, the Doctor had to have someone with him to be talking to. Hence the need for a.n. other to be in this ep. The thing to remember through the whole of the rest of it is that what's in the TARDIS is what the TARDIS has made and chosen.
It startes with the crash... the Doctor blames himself. But the next words we hear inside the TARDIS are those of the 9th Doctor reminding us that the hoards of Gengis Khan can't prevail against the TARDIS doors. The crash happened because the TARDIS meant it to. More than ever we're reminded that for 900 years she's taken the Doctor where he needed to go (and seldom where he wanted to go!). Clara promptly burns her hand on a Thing. A TARDIS thing... made by the TARDIS for exactly that purpose.
There follows the romp around the interior. Yes, I was disappointed at the lack of old control rooms. But let's be realistic: they decommissioned the 2005 interior and exterior as inadequate for HD filming. Some of the sets we're talking about were built for black and white TV with 405 lines. I doubt they'd be usable! (Though many do exist still in the exhibition). The glimpse of the swimming pool was a nice nod, but sadly still no bathroom. Nor a look at Rory and Amy's room with the bunk beds, which would have been nice.
Then Clara finds the library. With a stonking great book on a lectern. I was unsure at this point if we'd stumbled into Narnia and were about to make the Dufflepuds visible or were in an attic with Bastion reading the Neverending Story. Had we been in Wonderland, it would have had "Read Me" written on the covers in gold letters. And Clara, being chased by scary monsters and lost in the bowels of the TARDIS stops and takes the time to read a big book. Honestly? (One of the more unbelieavable bits IMHO). The book, like everything else, is made by the TARDIS. (Remember the key scene... she can make anything) Who else survived the Time War? The Doctor would hardly write his memoirs and include all his secrets, and leave it lying around for companions to read, even if an autobiography might assuage his survivor guilt. The other Time Lords are Time locked, and the Daleks have never struck me as the literary creative type (Dictate! Dictate!) The only other 'person' to get out alive is the TARDIS herself. And who else knows all the Doctor's secrets?
The scene with the Eye of Harmony and the scary monsters was the weakest bit (and a sop to those who like big visuals I suppose). I can't imagine any process that would leave one alive with red glowy eyes (apart from a political poster or two). But at this point our extras have become redundant, and we have to get rid of them.
There follows the one-to-one with the Doctor and Clara... of which everyone is crying foul that she lost her character development at the end. Excuse me? This isn't about Clara. The key item here is the Doctor's discovery. The empathic woman last week told him Clara is just an ordinary human being... finally the penny drops and he accepts it. Clara - this Clara at least - is just an ordinary person. Exactly how or even if she relates to the other Claras is still to be explored (and there were hints about blood kinship calling through time last week). But Clara is no mystery.
So, development done, time to round it off. With a hearty fun-poke at the people who complain about episodes having a reset button by using a genuine Big Button. Only this one is NOT a reset button. The purpose of the Salvage Bros is surely to shout loud and clear that things are not quite as they were. The reset is partial, mostly, but not quite the same. We have moved on. The Doctor tries to do something clever, throwing the button into the time crack, before realising that this is the work of the TARDIS (in Wonderland, the button would be maked "Push Me"). She has set the whole thing up for her own purpose, and now is setting such bits as she chooses back.
As for Clara, you can't signal more clearly that she's not quite the same than by having her wearing something completely different. Exactly how much she remembers from the Big Book remains to be scene. But she's not quite who she was. And the Doctor's understanding of her has changed.
Now, exactly why the TARDIS wanted all that is the interesting question. I just hope Moffat doesn't do his usual trick of throwing up a load of questions and then abandoning them in favour of something shinier.