I watched the entire series (so far) recently, and I really loved it for the most part. The storylines are truly ingenious, as are the twists they usually pack - and you've gotta admire any tv show that can induce multiple existential crises.
My two favourite episodes so far would be Fifteen Million Merits and White Bear. The former was a slow burn, but the last 15 minutes or so was one of the most devastating things I've ever seen on television, and the latter was incredibly suspenseful the entire way through, with a truly genius twist that recontextualised everything brilliantly.
The National Anthem and Be Right Back were also brilliant (hell, reading a synopsis of The National Anthem is what made me check out the show to begin with, and it definitely did not
) - the latter in particular really got to me, because the motivations of the main character were rooted so deep in my own greatest fears, their actions remained completely understandable no matter how insane the story became.
I wasn't particularly impressed by The Entire History of You or The Waldo Moment, though. Both had decent enough ideas (particularly the former, which could've been something incredible had they taken the idea of the memory-recording technology and applied it towards something more interesting than a bland plot about trust in relationships), but their execution really
left something to be desired.
White Christmas was also great, though I couldn't help but feel that Brooker was trying to pack too much into one special. There was definitely enough in here for at least two proper episodes of the show, and it would've been nice to see some of the ideas explored a little further (namely the concept of "blocking" people in real life, and making digital copies of one's consciousness to do minor tasks for them).
Overall, however, the show's resonated very deeply with me, and I'm really looking forward to season 3.