To be honest, I have no favorite feature in this release. It's all minor stuff in my opinion, ok, it's some "polishing" and "refining" which is great. However, it's nothing really essential like the upcoming REST API will be!

I really hope for REAL refining and polishing in future versions, for example in these areas: the search functionality, Multisite/Network improvements, export/import improvements (timeout issues, media issues), plus handling of wpautop in a lot of situations.