In the Confidential, Neil explained that for him the core of the story is at the moment when the Doctor and Sexy (a.k.a. The TARDIS) are arguing - he complains that she (the TARDIS) has never been reliable, never taken him where he wanted to go - and she (the TARDIS) replies that she always took him where he needed to go. It in one statement resolves a riddle passed down through generations of Doctor Who watchers, and is a great moment.
But for me the core of the story was a moment later - after they'd finished building the Junkyard Wars TARDIS Console and the Doctor couldn't get it to work and she says "You beautiful idiot, you have what you've always had, you have me".
The theme of this story appeared to be about male/female relationship and the beauty which can come when male/female relationship is perfectly bonded. Or, the ugly things that can be buried inside a male/female relationship.
That is - the story contrasted three pairs of male/female relationships.
a) Auntie / Uncle: We don't know them very well but they appeared to be close mates. But maybe The House made them be that way together.
b) Doctor / TARDIS / Sexy: This relationship between the Doctor and the TARDIS is not one I ever thought of before but with this episode it's obviously there. How do you live with a sentient machine for 700+ years without forming a kind of bond with it? We modern people move from house to house from time to time, but the Doctor and the TARDIS are inseparable. At least until some evildoer tries to take the TARDIS away, and some have but he always retrieved it. In any case we saw two beings who are very much in tune with one another.
c) Amy / Rory: Here though we saw some inner imagery between them played out by The House which indicates some stuff between them? That is - they were running around inside the TARDIS after The House took over, and were put through some horror scenes with Rory apparently having anger against Amy. It's possible the House just threw them into those scenes out of his own cruelty, or it's possible the House read those images from their mind using those against them.
A thing we learned is that TARDIS's touch every point in time and space - but we knew that from The Big Bang.
It was interesting to get various perspectives - did the Doctor steal the TARDIS or did the TARDIS steal the Doctor? It's a point of view isn't it?