Hmm. Some good bits. Some poor bits.
Biggest problem is that I'm not convinced by Clara & Danny's relationship so a journey into the underworld as per classical mythology or Bill & Ted's bogus journey was rather underwhelming.
I'm not actually sure how to vote at the moment. I think I'll need to take the episode in context with next week's conclusion as if you had asked me 20 minutes in, I'd have said poor, but it all became a bit clearer as it went on.
The master reveal I wasn't keen on. But it could have been worse.......