I know this is a minority opinion, but I absolutely loathed the episode. Even the episodes where I see faults, I still enjoy watching the episode, often multiple times, or at least find something to like. But this one I hated.
I'm sick of the writers trying to make Clara 'Oh-so-important' all the time. She was there for every single doctor, she was there when the button was pressed and said the words that saved Gallifrey. She's meant to be some child of destiny hand picked by fate to save the doctor as some sort of surrogate mother figure.
Its not just a clara thing, Rose, Donna and Amy were also these wonder-companions who had some predestined thing through their travels.
And now Clara is the monster under the bed and comforted the doctor as a kid? Really? She couldn't be just a normal companion now the trinsalore arc is done? Nope, she's still the special child of destiny.
And the companions being so important to the universe makes the episodes weaker in my view. It reduces the tension knowing that they aren't really in danger because the universe needs them alive.
And (separate unrelated point) clara being this caring figure who checks the bed for monsters to the child version of the guy she was just on a date with is creepy as hell. Given that most of the episode dealt with the character as a child, that creepiness extended through the episode.
Complete lack of self awareness when an old man looks a child in the eyes and says "you should be scared" as he's in the child's bedroom, from a guy who has spent enough time on earth to understand that randomly appearing in a child's room is weird.
The pacing was all over the place and the end of the universe thing seemed to come out of nowhere. And the Doctor would surely remember that HE WAS THERE AT THE END OF THE UNIVERSE! Utopia! The end of the Martha season, with the Master and captain Jack!
And there was so much they could have done with the concept. It could have been the return of the Vashda Narada. The silence in the library monster. They were terrifying. I feel they wasted a good concept. The thing we speak to when we talk to ourselves.
If the majority of the series is as good as the Dalek one a couple of weeks ago, then Capaldi may well become my favorite doctor, but if there are more like 'Listen', I'll probably stop watching. I don't want to be one of those fans who hates the show I'm watching.