The show is well done over all. It's a bit over the top, but that's on purpose, in order to make the points go across. I don't have issues with the quality of what I saw, I thought it was pretty good. My problem is the points it's trying to make.
Black Mirror's main character is technology. It it the only recurring character, as the human characters are always different, and the future (or present) they live in is also always different. The characters in Black Mirror are confronted to new technologies in extreme ways (for example, someone who lost her fiance to a car accident buys an app that recreates her fiance's online personality from what he wrote on facebook&co, and then proceeds to "chat" with it), and you're supposed to draw conclusions from it. If I were to summarize the message of the show, it would go something like "We're having a ton of progress, but humans are flawed, so there are issues with it."
Wtf kind of logic is this? That's not how you debate. You're showing anecdotal evidence where things went badly for someone, and this is supposed to make me think twice about the big picture? You're basically raising issues with technology because in some situations mistakes will be made. A more accurate account would be that the problem is on the side of the people making the mistakes.
Let me use that line of thinking for things we have today. Cars. Cars are very bad! People died in car accident, so we should have a discussion about the negative effects of cars... That makes no sense at all. We blame reckless driving, not cars.
Also, I have a general issue with the sentence "This is why we can't have nice things". For a few years, it's been fashion, especially in TV shows, to criticize humankind. We are flawed, we are imperfect, we make mistakes, we are human. We don't want a perfect hero like Ned Stark anymore, because they're too good, we'd rather see grey, imperfect people. That leads to a negative message about humanity, because you know, when you're not good people, you can't have nice things.
But that's actually not true. Yup, humans are flawed, humans are clearly not the perfect little beings that some portrayals would have them be. And that's okay. We can have nice things anyway, and we do. All the time. I wish more shows would realize that.