I've read the reviews complaining about it not being black mirror or the episode being boring.
What were you watching?
Black mirror is all about technology affecting our lives in the near future and showing us paths that may be trodden.
This is about the perils and highs of immersive gaming, this is about better than life (thank you Red Dwarf), this is about boundaries being blurred, relationships being blurred, life being blurred.
Nothing in this episode couldn't happen and very likely will happen.
The cast was strong, the writing and direction both strong, ending strong.
This had it all.
Writing this review I changed my score to a 10 from a 9 as I couldn't see what was dropping the point whilst I wrote.
I've intentionally not put any spoilers and the hints I have given were in the trailer.
It's a great episode. I have no idea what the negative reviewers were watching to be honest.