Death In Heaven is either one of the best episodes of the series, or one of the worst.
This depends on what you as a viewer feels about the blatant pulling of their emotions.
While in the episode prior, we only had a (delicious!) taste of Michelle Gomez's terrificly demented The Master (or - as 'he' is currently a 'she' - The Mistress), here, Ms. Gomez is at full tilt crazy, and what fun - and thrills that entails.
The episode also gives a really terrific farewell to to Samuel Anderson's Danny Pink - who a lot of people had mixed feelings about (personally, I felt the relationship between Danny & Clara seemed forced - they really had no initial 'anything' to make Clara seem to make hooking up with Danny so important).
In the previous episode, we find out Danny had been killed crossing the road - right after Clara expressed her undying love of him.
Here, we find out that Danny - along with all other deceased - are being turned into Cybermen.
The thing is, the inhibitor Cybermen have - that circular plate on the centre of their chest - which controls (suppresses) their emotions, isn't yet activated, and Danny - unable to being dead, a Cyberman, and unable to ever again be with Clara - asks her to activate it.
The Doctor knows the instant the Inhibitor is activated, 'Danny' will cease to exist, and an unfeeling, uncaring Cyberman will be In his place - and kill Clara & then - on Missy's plans - kill all of humanity.
I'm writing a review - not the plot, so, what happens, requires you to watch.
What I will say is that the dead Danny is given a chance to return to life.
It's made very clear - by the actions of Clara in the beginning of the prior episode towards the Doctor - how deeply she feels for him.
What Danny does causes a huge emotional change in Clara - and what she wants to do with her life.
As I like Doctor Who, and don't like spoilers told to me, I must've missed the announcement of Jenna Coleman's departing, so, the ending scenes really came hard at me.
Apparently, we haven't yet seen the last of Ms. Oswald, as a surprise visitor - during the end credits - makes clear.
Until Christmas, '14, this episode will be the series proper's conclusion.
I agree some of this series' episodes have been hit or miss, but, I think Mr. Peter Capaldi's portrayal of the 12th Doctor has been wonderful
I hope - and believe next series will only be better.