Meandering Pre-Review Opinion...
One of the very worst things a creator should ever do is destroy the mystique inherent in his work. I always call it "Romulan Syndrome" because they were the mysteriously cool villains of Star Trek, right up until they were overused and made mundane because of it. Fans are fickle, awkward, occasionally stupid creatures. They want more information about things that sound cool. Romulans, Breen and Borg from Star Trek, the Future War of Terminator, the Clone Wars in Star Wars and of course the TARDIS in Doctor Who.
Wanting to know more, discussing the possibilities, daydreaming about these things is fine. But then a writer, or worse a movie executive type decides to give us these things that we think we want... And the end result is almost always horrible. Terminator Salvation anyone? The prequel trilogy! Nero, the dumbest Romulan of all time...
Oh, and stupid Journey to the boring Centre of the miserable goddamn TARDIS!
The Review...
Well, that sucked.
...
Oh fine.
The Real Review...
It DID suck. The inside of the TARDIS could only ever have been a disappointment, and it really was. The whole episode was running around in cheap looking corridors. Inconsequential supporting cast members. No-one had anything to do except run! The conclusion was a pathetic cop out and even by 'Who standards the rules of time travel served only to obey the whims of the writer, the bloody appalling Stephen Thompson (responsible for the awful "Curse of the Black Spot" from last season) by the way.
But! And there is a but... I will credit the few good aspects of this otherwise terrible episode. The molten monsters (called Time Zombies) were cool looking in a Silent Hill-esque way, especially the Doctor's future-self with his hand attached to his face. Creepy.
Sadly, that's your lot. The rest of this episode was so much unsalvageable junk. I'm sure at the pitch stage exploring the TARDIS seemed like an interesting idea, but someone along the way should have realised the execution was going to be difficult, especially if you wanted the end result to be good.
We've had two bad episodes now, let us hope that is the end of it and the series can get back on track.