A real "timewar"?
When reading the comments and checking the episode myself I have to wonder if we're not having a real timewar on our hands: that of the generations. It looks to me as if a majority of younger viewers seems to like the episode whereas more seasoned who fans don't care for all the "shallow" (action) twists.
And I have to admit that I'm also cynical. My main gripe here is that the popularity of the series has heavily declined with the last season and as such they needed to make this work. My main dilemma is simple: when is something a harmless tribute and when does it become a shameful attempt to share in the others popularity? This episode is surely testing that dilemma because its "borrowing" settings from all over the place. From Star Wars right down to Ghost in the Shell. And I'm not sure I like that approach because Doctor Who should be setting the standards, not borrowing them.
Then another issue: plot twists. Collect everything good about Doctor Who (Master, Daleks, time based plot twists and a bit of obvious mystery), add some spectacular scenes even if they are plain out ridiculous (tank scene) and you'll end up with this episode.
The main reason I'm a bit meh myself is because apart from heavily borrowing plot twists from other work out there the series is now also heavily contradicting itself. There was once a time where the doctor was careful with influencing the time stream, this was even made obvious when he brought Vincent van Gogh to a modern museum. Yet now we roll tanks into ancient history, leave people to wonder where the electricity for the guitar is coming from and we don't care about the possible consequences. One would say nicely dramatic introduction, I can't help thinking: "fillers".
And so we enter the real timewar: the older generation who lived the Doctor Who history and who valued some of the serious parts in the series and the younger who are more drawn towards the more action and less serious (dare I say shallow?) approach, at least that's my impression of it.
Yes, it was enjoyable to some extend, but I also think the overall quality dropped a bit. Especially if you start using other peoples popular work in an attempt to repair the decline of yours. But of course people like it. The modern generation is, after all, generally more centered around itself and doesn't really care too much of their surroundings anymore. Who cares if I bother others when I park my car here, I should be allowed to, right?
SO yeah, I say a battle of the generations.
Personally I foresee an enjoyable yet incredibly shallow season.
We'll see :)