However, you noted that the IT department (assuming IT and engineering are separate at Netflix) was overboard with firing. If the manager on Glassdoor worked there, do you think his review is more justified?
Netflix's pronounced strategy is great if you have judicious and fair managers all the way up the ranks in your department, but it seems that it only takes one bad manager to spoil a large bunch of good apples; overall performance is a pretty subjective metric after all, and if you get a particularly closed-minded or prejudiced manager (and such people are plentiful in the IT and engineering sectors; those of us who work with absolutist machines all the time seem to inherit a bit more of their habits than might be desirable) and he gets annoyed at something about you or your work, I doubt it's a very long walk from "awesome excellent performer" to "adequate performer" and a severance package for your average employee.
Does Netflix have guards in place to protect against that? Do you think that the situation the reviewer described could have occurred in the same company because his department had a more difficult manager on the loop? Do you think that you've stuck around because you share the views or preferred styles of the other managers, which thereby makes you "super great performer"? Do you think that the Netflix policies have a tendency to create a useless feedback loop of yes-men and groupthink?
The problem with running a programming team like a sports team is the difference in transparent metrics. There's a few simple measurements for the value of an athlete, depending on perspective: if he has good name recognition, he is a valuable business asset, even if he's not really a high-scorer; if he scores a lot of points and puts your team over the top often, he's a good asset because he increases the value of your franchise by making it win more often, and so on.
The metrics in engineering, especially the day-to-day engineering of going into work, working on programs, and then coming home, are much less clear.