Black Mirror is one hell of a ride if you like futuristic sci-fi. This episode is one of the best minimalistic stories I've ever seen. It's in black and white, which I love, but here it makes everything bleak, adding to the tension.
I found myself literally on the edge of my seat. I also like that they didn't spend any time explaining the world or trying justify the story. They just dropped the viewer in and let them experience it. My reaction was so visceral I had to turn the damn lights on.
My only quibble, and don't read on if you don't want a SPOILER---------
I'm giving you the chance to look away---------------
Okay, calling those things dogs? No, no, no. Those were fucking metal cockroaches. Just saying. They had that sleek body and they just wouldn't fucking die. *shiver* Watch this one with someone you love so they can comfort you after.