I wasn't too impressed by E01 ("USS Callister") and E02 ("Arkangel"). Then I saw E03 ("Crocodile").
E01 "USS Callister" was fun because of the whole Star Trek look, but it wasn't very well thought through. They had an idea, and decided to wrap it up in nostalgia. Even the scifi part of it was quite crappy.
E02 "Arkangel" was a step up from E01, but the episode was always on the brink of going somewhere interesting before deciding to stick to the expected and predictable (like in last season's episode 3 "Shut Up and Dance"). And predictable isn't good in this anthology setup.
E03 "Crocodile": Holy fucking intense! Now this is what I wanted from a Black Mirror episode (even though it lacked the dry humour of the British episodes from S01 & S02). But bloody hell, this was a great mix of the dark-side of human tendencies and scifi.