As one famous Japanese general once said (
@haitch40) "Everything is a dream within a dream" - was this episodes theme. I think???
Standout thing about it was the line
"Alien? You have a film called alien? No wonder everyone wants to invade you!". Other than totally meh for the most part. The dream aliens were kinda scary, and in a main series the kind of thing that would deserve a 2 parter, but otherwise, just no. Clunky and confusing. Moffat give Capaldi a damn good screenplay and more of a chance next series, because this was to me, poor.
However I hear Missy is back next series. Thank goodness, she was the one spark in 2014. Whatever you say of a female master, she sells the role brilliantly.