Doctor Who has become a shadow of the unique and shining thing that it once was. I guess when you start (or restart, as it did in 2005) on such a high note, there's only one way to go.
This year's Christmas special, in which a new actor* was introduced, broke several major story-writing concepts. Such as: show, don't tell - this one's really fundamental and breaking it to allow the bad guys to severely outflank the good guys without a hint of the danger is just confusing and dis-interesting.
A second rule broken: failing to make people care about the central characters (or their passing). Main character? Don't care. Main supporting character? Not sure I could describe her accurately. Other characters? Disposable cardboard cut-outs.
A third rule: don't introduce Macguffins and then not use them. The classic rule is, if you show a shotgun on the wall, you have to fire it off. It's not iron-clad, but why the hell introduce a "truth field" in a science-fiction story and then drop the idea without the slightest use or consequence?
And then there's needless "retconning" of an entire species. The Silent were creepy and powerful when they were an unknown quantity, for very good reasons invisible and of intentions unknown. Explaining them was not only unnecessary but the explanation given was both in itself stupid (oh, they're Priests from a human church? funny how they went about enslaving humanity while supposedly fleeing some great disaster) and, unless I'm mistaken, done in a way that directly contradicted a previous back-story. What happened to all of that business about the Silent being among several races fleeing the portion of the Universe (that was being destroyed just two seasons ago)? Again, if they hadn't already broken the rule about making people care, I'd look into this a bit more but it was just weird.
Which brings us to the most egregious "retcon" to date. The repeat return, without explanation, of the Daleks. The entire back-story of The Doctor is that he had to imprison his entire species because it was inextricably tangled in a total war with the Dalek. Imprisoning both mighty species was the only way of ending a war that threatened to destroy the Universe. Which, as a story, stands.
The Dalek keep bloody turning up all the time. And I mean, in all of time, wherever Doctor Who goes, he stands every chance of running into a Dalek. Or ten million. It breaks the entire premise of The Doctor's character if he's imprisoned his own people while their enemies are free to zip here and there through all of time and space.
In all, it was like seeing a funny but muddled Doctor Who fan-fic written by high school students. I could go on and on (e.g. introducing interesting characters who are then never seen again - that's just annoying and no amount of witty dialogue can paper it over) but I'll stop. I'm somewhat glad that there won't be more episodes until the Autumn. The show's been increasingly out of control for quite some time now. It's gotten past distraction, it's now a hopeless mess.
*I have high hopes for the new guy, but suspect that a new writing team is required to pull it off.