For some very odd reason, the title sequence can't make its mind up on whether it wants to be in sync with the theme, or not. Eps 1 and 3 are out of sync, 2 and 4 are in sync. Very bizarre.
So, I've three eps to talk about, I'll talk about 3&4 at once since they're a two-parter.
Really enjoyed the second half of the Dalek episode, The Witch's Familiar.
[The Clara/Missy dynamic is still pretty good, so much so that I might prefer it over the Doctor/Clara dynamic. Very chilling how Missy almost managed to make the Doctor kill Clara when she was trapped inside the Dalek, though I do wonder why Clara hadn't considered thinking about opening the Dalek shell herself, given how simple the suggestion seems to be. Missy's final scene, getting cornered by some Time Lord Daleks, makes me wonder if she'll be seen in an alliance with them when we next see her.
Of course, the best part of the episode is the interaction between the Doctor and Davros. "The only other chair on Skaro," had me chuckling quite a bit. Then there was Davros playing the Doctor, and us. Blimey, considering how bombastic and hammy Davros was in the Series 4 finale, I wasn't expecting this moment to be so heartwrenching, but it was very well played indeed. His plan was pretty nice too, but I can't help but wonder as to why he didn't consider the Dalek sewers, or did the Doctor somehow modify the link so that his regeneration energy would go to them?
Anyways, it was a strong and well needed start to Series 9, I was a bit nervous beforehand due to my disappointment with A Death in Heaven, which kinda fell short for me after the set-up in Dark Water.]
And then we have the Under the Lake/Before the Flood two parter.
[Not really scary, but I don't think that was the point. Definitely did like the sense of mystery about it. I find it interesting how this episode makes a point about Clara's addiction to being with the Doctor. Makes me wonder how that'll turn out moving on...still, she's not gone completely Doctor, given how she prompted him to use cards to convey sympathy.
I did also like the Fisher King's design. Possibly one of the best looking non-recurring monsters I've seen in NuWho at present. Pity he doesn't get much screentime, because he looks awesome, in the literal sense.
The supporting characters were pretty good too, I don't think this episode would have been anywhere near as good if they weren't played as well as they were.
That being said, I'm finding it kinda difficult to write about this one, it had a nice plot, but I don't really know what to say. I did like the intro to the second episode, as Shroobie mentioned. Nice bit of fourth wall breaking that ended up being relevant to the plot, but not in a Deus Ex Machina sense. Also liked how we got to hear the theme with a guitar backing. Actually, question for the musically inclined, was the Doctor actually playing the guitar?]
EDIT: The intro for Episode 4: