Have just managed to catch up on all this today. Overall I actually really loved it, far more than I was expecting to (wasn't that impressed by season 3).
Loved the horror elements and the more darker tone in general. I adored the backstory this season.
I agree though how several of the characters are seeming like spare parts now with no real relevance to anything. Robin and Will being glaring examples, and even Mike, although I predict he will come into play more in the last two episodes of this season.
Actually it is interesting how they're being a bit less subtle about Will's sexuality and crush on Mike now, though whether they'll actually confirm it by the end remains to be seen. I can just see Will getting even more forlorn. Come on Will, you can do better than Mike, he's a rubbish boyfriend anyway.
Not keen on the blatant hinting at Steve and Nancy that seems to have appeared out of nowhere this series not just because Steve is mine. I just don't really like the idea of them together anymore; she and Jonathan had so much more chemistry. Actually Jonathan's another character they've done sod-all with this season.
I love Dustin, he makes me laugh so much. And Max has been brilliant. There was probably other stuff I wanted to mention but I've forgotten now. Gutted we have to wait until July for the rest!