Before I get to the more obviously controvertial points, the script itself was terrible. The opening basically wasted the character of Danny, meaning either he's dead, in which case it's a complete waste of potential, or he's coming back, which undermines the death scene in the first place (I'm tired of the 'Everybody Lives' moments being the norm, and I thought this series was starting to move away from that.). It was also ploddingly slow, the first half an hour painfully dragging and the last ten minutes far too rushed. It's been so long since they've done a 2-parter that it seems they've come to think it means half the pace rather than double the content.

Clara's ranting was completely out of character, and to a certain extent, so was the Doctor's reaction. While I liked the 'did you really think I cared so little that betraying me would matter' line, the rest was just badly written and poorly thought out.

Now, the Master/Mistress/Missy/Whatever we're calling he/she/it/them from now on. Ignoring for a moment the fact that the regeneration and gender swap was pointless, unfounded and at the moment inexplicable, the reveal was too poorly done. There was no set-up, no building and time to theories, it was just BAM there's a scary woman who's a droid BAM she isn't a droid BAM she's the Master BAM What the hell? Compare it to how they built up the reveal in Utopia, a really great episode, and you can see how this one is a seethrough-pale imitation.

And making him a woman, why? Unless they have a bloody good reason for the change next week, it's simply either a token gesture to the minoroty clamouring for a female Doctor (and can you imagine the noise they'll make next time now a precedent's been set?) or it was an attempt to be 'different' that fell completely flat. Like it or not, the gender of a character is as much a part of that character as their background, history, relationships and attitude, and to make the Master a woman just for the sake of it undermines completely one of the most established and defined villains in sci-fi. Like I say, there better be a damn good reason given or it's just pointless. And don't get me started on why/how the Master is using Cybermen as footsoldiers...

So yeah, that's why, and I expect I'll give next week about 10 mintues to make up for it before I turn it off. For the first time since it came back, I'm considering not actually watching the next one and hoping things pick up for Christmas.

Regarding the Master's gender: hasn't it already been established that Time Lords can regenerate into different sexes? The 11th Doctor at a certain point mentions the Corsair, who has had both male and female regenerations.

Yes, it is written in The Doctor's wife, but I believe, off-script, the writer Neil Gaiman hinted that it was a conscious choice or at least a subconscious one, and that The Corsair was already transgender. Of course, whether you take that as canon or not is your own call to make. The other thing to consider is that it can't be random, as the Dr has gone through a a dozen regenerations and got a man every time, presumably not through some coincidence.

Personally, I don't think it's something that can't be done, or even something that shouldn't be done given the correct circumstances, but in the Master/Missy's case, it just strikes me as Moffat throwing it in in a sort of 'shock for shock's sake' rather than for a reason. If there`s a good enough reason for the change given next week, I may have to reconsider, but if not, I'll still think of it as typical Moffaty 'look how clever/bold/shocking I'm being today!' One almost-credible theory I've seen is that the Master has stolen another body purely as a means to survive, which would be in character, but I think I'm just clutching at straws to save one of my (maybe soon to be former) favourite characters here.