I think we can talk spoilers here, but if not, mods can delete this.
My son (11) and I binged the whole thing today. The last episode killed me. Got super dusty. I really enjoyed the whole season. A few random thoughts/observations:
I'm glad they let Billy redeem himself at least somewhat. I'm sad, however, that there will be no more cocky lifeguard Billy. Because I wanted to see more of his...character development.
My son predicted Billy would die because the main deaths in the previous seasons were also characters whose names started with a B. This prediction led us to the tubes to figure out what Hopper's first name was because neither of us could remember. (It's Jim.) This gave us temporary relief, but when he and Joyce made their date plan in episode 7-ish I figured something bad would happen to him.
Loved Erica, although her character was a little cliched.
Dusty and Suzie singing the theme from The Neverending Story was fantastic, as was her giving him shit about not knowing Planck's Constant. "Phoebe Cates, but hotter." LOL.
I'm glad we got more Murray this season.