"Well, here we go again!" -- Madame Vastra
[Warning: There may be spoilers here]
TL;DR: 6/10. This is Sloppy Moffat. Not at his worst, but still sloppy. It's saved by several excellent performances from the main cast.
This is a companion discussion topic for the original entry at http://ghost.radiofreetomorrow.org/2014/08/24/doctor-who-s8e1-deep-breath/