I've been rewatching the earlier seasons this past week or so in preparation for S4 P1 to drop on Friday. I started S1 on Saturday night, finished it Sunday afternoon and go through S2 on Sunday and Monday nights. I've got work tonight, but S3 will be watched over the next two nights.
Gotta say, S1 really holds up well. If it wasn't for the dangling threads at the end, it could've easily been a great self-contained single-season series, but of course we've gotten way more of it. The second season is a bit hit-or-miss for me. I liked all of the character development, and the new characters in Max, Billy, Murray, and Bob, but the pacing is a bit all over the place. Then there's the highly divisive 7th episode, "The Lost Sister", which I both like and dislike - it's great world-building for Eleven and where she came from/what she can do, but it's an episode that could've benefitted from being one or two spots back in the season. It also would've made her visions of Hopper and Mike feel more like a cliffhanger (because we've already seen them in the previous episode, but it would've been neat to see them without context first), and it would've also made her return in episode 8 a LOT more triumphant, especially if we don't see her taking a bus back to Hawkins - just leave her after the police gunfight with Kali and her gang.
Over-all, Season 2 was a step or two down from the first, but still really good. I loved what they did with Steve, and find it fascinating that they split the party up as much as they did, allowing for some new character combinations to develop throughout the season. Can't wait to rewatch the third season!
-Marc.