Well, that was great and confusing and weirdly paced and funny and unexpected.
I liked it, but it was too much. You expect a two-parter to be able to breathe, but apart from a very brief exposition scene when they are transported by Davros' servant that calmed things down, it was a far cry pacing-wise from recent Moffat-episodes such as Deep Breath (the second half, specifically), Listen and Dark Water.
Visually it was brilliant; they've once again upped the ante in terms of lighting, and I thought the effects (especially the snake reveal) looked great. Individual moments and scenes such as Capaldi grinding that axe like a boss, Sarff sliding through that Cantina-esque place containing some familiar alien faces, and the pre-intro sequence were really enjoyable. In general the beginning of the episode was really good, but the swift changes of locales, the sometimes confusing plot and dialogue weared on me a lot towards the end.
I hope the second part slows thing down (though it's most of the time the second part that is the most fast-paced, so I don't know what to expect), because I think this story has some great potential to end up being more than just good.