It was interesting and kept my attention.
It was clever to see Clara put in the position of the Doctor, but it remains tiring that Moffat's series remains focused on Young Girls And Their Lovers Who Travel With The Doctor.
Clara's hardly young anymore and the 'lover' aspects only usually come up as they are about to leave - it seems to be thought of as acceptable the women companions should choose to leave Who for love.
I thought this was a great episode, it really creeped me out more than a couple of times with its creeping walls and flattening of people etc. Great resolution too with the painting of a door to trick them to channelling their energy into the TARDIS. The effect on the 3D boneless wasn't bad either.
The Doctor poking out of his mini-TARDIS and passing implausible items like a mallet and his dimension gizmo, and the "Addams family" moment was hilarious (even if I can foresee the steam from TEIN's ears!!) - when did the Doctor sit around and watch the Addams family?!
Missy tagged on the end again, watching Clara on a tablet and saying she's chosen well.... still fairly unclear what Missy has done other than drink tea and eat cake, but her plans must surely come to the fore pretty soon. And they involve Clara, which is a shocker, narratively
Missed the Adams family bit - But yes it isn't required if they want to maintain credibility. Factual TV reports would be OK though. Mixing far fetched fiction in far fetched fiction doesn't, work for me.
I really liked this episode: having 2D monsters lurking unseen on any surface is genuinely creepy; lots of amusing dialogue**; there was enough running about to keep one from thinking too hard about the science, but it was running for a purpose (escape), not just a random panic; I was (vaguely***) reminded of the Doctor series set in abandoned Tube tunnels. And in all of that, we get a (nicely revealed) better understanding of how the Doctor thinks about himself and what he does.
So it was exciting, informing, funny and creepy. What more could one ask (unless you're TEIN) from an episode of Doctor Who?
** - Though on thinking about it, I'd have liked the "nasty" Doctor to have replied, "It's called the Toodis. Are you 2-Dim to think of that, Doctor?"
*** - Vaguely because I can barely recall that series.
Wasn't that a Left-bridge-Stewart episode with the yellow maggoty things?
Well!
If we allow the shrinking Tardis and it's ability to be overcome by a two dimensional universe which I had trouble with given that in a country full of blind people the one eyed man is king etc. Plus the
one thing the Tardis is able to control it's own shell. So putting those to one side.
I thought passing the items through the door worked well (given the above). The items themselves were a bit dodgy though.
Not sure what was going on with the magic pass and the Auf Wiedersehen Pet guy that only saw a blank sheet (I think that's what he said) Anyway it didn't work for him. (bearing in mine the pass is daft anyway).
I thought the actual basic plot was at least original - well to me at least. The rotating images in the tunnel was a bit naff, but it was consistent with the plot idea. The painting that couldn't be restored was even a nice touch and well revealed by Clara. On the hole probably the best one of the series.
BUT>
I thought the shimmering carpet and floor surfaces was a bit jarring, although the actual death (Especially the WPC) was quite well interpreted.
We have a lot of introspection by Clara, as a result she becomes to understand the inner workings of Who's world. We have Clara running around saying she is Who. Is that a tester for the next Who being female. (As in Time Lords live twelve male Who's and then twelve females - twist) We have the reveal about Clara being a lying bitch about how Danny is OK although Who discovers Danny isn't. (Although I thought he was or gave the impression at least).
Then we have the obligatory ending scene of the mysterious woman. My son left the room in disgust saying:-
"Oh and the best piece of equipment in the known universe happens to be a computer tablet from Earth - circa 2015." Or words to that effect. Was that really product placement?
In conclusion - Acceptable.