I am through three episodes of When They See Us and yes, it is extremely good and essential. The first two play like an episode of Law & Order but instead of making the detectives and DAs into heroes, we see them for the corrupt monsters they actually are. I quibble with a few aspects of how they present the trials because they make absolutely no legal sense (the prosecution is shown resting at a point where things don't look great for them, yet for some reason the defense actually bothers to present a case which seems to open up the worst evidence against their clients).
The third episode feels a bit off in the context of the first two. It does useful work in showing the challenges of post-release life. But whereas the first two episodes specifically group the kids together into one story, the third episode largely sends them out, now as adults played by different actors, to have their own individual stories. With new actors in the roles, it feels like the show needs to reintroduce us to these characters. The actors don't look enough like their young versions that I automatically know which relates to which, so I felt I needed more somehow, but everything was so spread out it didn't get there. Of course, there is a very good reason they couldn't get all of them together as a group in the episode.
Anyway, looking forward to finishing this tonight.