As for the new Doctor - I thought he was great. Capaldi already appears to be the antidote to the "fun" Doctors of recent times and is definitely the refreshing change of Doctor that was needed. His acting was actually very good (although I detest the silliness that we have to put up with after every regeneration, it's just not funny in my opinion - it wasn't quite as cringey as the fish fingers and custard thing though, thank goodness). He made the best of what was essentially a naff script.
As for the plot - diabolical writing. I get that some people love Steven Moffat, but for me, it was just one massive confusing mess. I kind of feel like the writers feel that the recurring story arc is some kind of excuse to go crazy and just start scribbling whatever they want down. One minute, it's a tense scene with Clara confronting the clockwork creatures, the next it's human/lizard lovers raining from the ceiling in ninja gear "in the name of the British empire". Bizarre. And it looks like yet ANOTHER crappy, complex story like all that rubbish about Demon's Run we had to endure. It's not that I like shows where I don't have to think - quite the opposite, in fact - but it's just utter tripe time and time again at the moment.