Yeah. I thought Season 4 (previous one) was really good. Probably one of my favorite seasons of the series. But, like most of the seasons of the series, I thought there was a pretty marked discrepancy between the best story arcs and the most middling.
In that case, I thought the stuff with Dustin, Lucas, Max, Steve, Nancy, and Robin learning about Vecna and trying to exonerate Joe Quinn's character to be, by far, the best, most compelling stuff in the season. Then, El trying to regain her powers- still very good. Then Harbour and Ryder in Russia- not bad but meandering at times. Then, Mike, Jonathan, Will, and the Jonathan's buddy trying to get from California back to Indiana, which really didn't amount to much in my view. That story arc didn't really land for me until they finally met up with the main protagonist.
I'm a bit surprised by the more lukewarm critical reception to the first wave of this final season but I can see some of the drawbacks you guys in this thread have pointed out. I still think it's quite entertaining and it at least seems to me as though the Duffer brothers are building to the resolution that they want rather than something like Game of Thrones' finale where it just seemed like a mad dash to a finish line that didn't feel cogent with all the buildup that had come before.
I've watched the four episodes so far and I think that there are again bright spots and some lagging elements. Millie Brown and Sadie Sink both tend to be terrific. David Harbour is great. Winona is fun to watch.
Mike was never a character I found to be that interesting in the early going but I have to hand it to Finn Wolfhard in that I think he delivered some of his best work last season (and so far this season) despite having that largely thankless storyline in season 4. He did a really good job in the scene after Eleven attacked the bully and in his big season-ending motivational speech.
At the very least, I think the performances of the young actors like the aforementioned and Matarazzo and McLaughlin, and the way that they sell the authenticity of their friendships is always effective.