I got to the end game part of the finale previously and have been holding back, wanting to finish so much else in the game and not wanting it to be over (even though I know I could do this in premium adventure as well). Pulled the trigger today and loved everything about it. It adds so much to the first game that it'll be hard to wait for Kiwami. I actually feel a little jealous of those that are experiencing the series this way because it provides so much more context and depth to the plot of the first game.
Amazing job by the RgG team to make a prequel this good and great job by the localization team.
Just as a heads up don't start the final section (you'll get a notification) unless you have a couple hours. Lots of long cutscenes, credits and post credit scenes you will not want to rush or skip.