I think i finished the season in binge-worthy fashion and this is semi- more coherent SPOILERS thoughts within.
I really enjoyed this season. It was dark, it was fun, it was suspenseful, it was well written for the most part. I thought the finale could've been better since i thought it left a lot of loose threads opened and it shouldn't have since finales should keep things tighter like how it was in Season 2 when Eleven came back to save the day and they ended with the dance which was cute.
I loved Eleven in all her bad ass moments, loved episodes 3-5 <3 (sauna test, Eleven looking into Billy and what he was up to with his bad moments), loved Erica! (she's a riot, really is), loved the quartet at the mall battling the Russians, loved Billy's backstory and quite sad he died at the end.
My favorite character (Will) didn't have many endearing moments unfortunately except for wrecking Castle Byers and also the only one without a significant other. It's sad his friends all have crushes and such and he's left behind with just wanting to play games. I was that way too! I don't want to grow up and liked to be young and "immature" as long as I can.
Loved Hopper and Joyce on their side adventure with the Russian and Murray. Didn't like that the Russian (Alexei) was killed.
Loved girl moments at the mall with Max and Eleven in the lighter moments, "you can't spell America without Erica" and all of Erica's lines were gold, and found the guys angsting about the girls funny.
Didn't like how they never explained Russian occupation and what they were doing with the green goo and why they opened the gate in the first place.
The Mind Flayer with the flayed were very creepy and I liked the intensity of that. The hospital scene with Nancy and Johnathan battling the flayed Holloway and newspaper guy was creepy as well and added a darkness and creepiness that seasons 1 and 2 didn't have.
Season 4 has a lot to resolve and lots to live up to. I would give season 3 rating of 8/10. It was up from when i first finished watching since i had chance to read up on internet spoilerage and explanation. :P
/edit
I don't think Hopper is dead btw. So i did not cry in last episode. The letter to Eleven was sad, i admit but i wasn't sobbing like other fans in this world. Hopper will be back.
Back to regular programming soon. This show is awesome! :)