No real spoilers, but a couple of non-specific comments on a couple of plot points. So... give this one a pass if you really don't even want a hint of a thought of a spoiler...
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It's on okay show. I do get why a lot of people think it's the best thing ever, so I wouldn't go so far as to say I think it's over-rated simply because I didn't like it that much, but personally I also found season one, especially the first half, really hard work, maybe because even in 1985 I was one of the few kids who really, really hated, and still hates, The Goonies, which Stranger Things is really set up to riff on. Watching groups of young American boys of varying levels of acting ability shouting excitedly at other does about how cool everything is did not a good movie make 30 years ago, and it doesn't make good TV now.
(Yes, Stand by Me is the exception that proves the rule!)
I do really like the visual design of the show, the soundtrack, and amusing 80s callbacks do always get a little smile of recognition. The Upside Down is a cool concept. I also think the adult sections of the storyline are mostly excellent (any scenes with Ryder and/or Harbour are the compelling ones which makes the show worth watching imo), although the biggest draw on the show is undoubtedly Milly Bobby Brown, who also utterly brilliant: a real future star there if she continues acting into adulthood. I like the Jonathan character too, although he's still a bit underwritten. The latter half of season one did pick up the pace once every character knew story they were in and actually started working together. So I came away at the end having overall liked the show and feeling it was marginally better than the sum of its numerous flaws.
And the main issue for me, and what caused most episodes to be a chore for long stretches, is whenever Mike's sister appears on screen. Doubly-so after she hooked up with bully boy frat dude. (Can't remember either name, and I watched the first three episodes of season two yesterday, in which both appear plenty!). No spoiler details, but her scene with Jonathan, involving a certain tree, in season one is a particularly notable sequence that had me rolling my eyes at the poor writing there. Some of those poor writing moments continue in s2: a sequence with El in e3 had me predicting the obvious plot beat it resulted in a good twenty minutes before it finally occured. Maybe the pay-off in e4 will be unexpected, but within e3 it played out in all too obvious a manner.
It also suffers, badly from what I call
Lost Syndrome.
Season 1 could have been 6 tight episodes long if characters had
told each other what was going on rather than keeping secrets for no reason other than filling up the episode commission. Season 2 seems to be continuing in that same tradition. Character A discovers something but doesn't tell character B some pertinent piece of information because plot. Then character A does tell character B, but Character B doesn't believe it. Character D has known all along. Then Character B independently determines that maybe Character A was right, but doesn't tell Character A that and they should work together. Character C knows everything characters A, B and D know, but doesn't tell Characters A, B, or D because they're a scientist, and all scientists are either bad, misguided or stupid.
The good bits make it a compelling enough show, but take away the deliberately retro setting and I doubt it would be quite as popular. It's like a decent two-part X-Files or Fringe* episode stretched out across 8 or 9 episodes by padding it out to a large ensemble cast.
*Heresy, but I vastly preferred Fringe