Interesting... if this works the way they designed it to (or, for the more cynical out there, "the way they claim they designed it to"), it'll shift SEO away from Google-bombing / keyword bombing and towards producing quality content. On the other hand, depending on how it quite works, it might end up just replacing the bomb site results with "most engaging" sites, which could be considered a net negative result, since I think we've all learned in recent years that engagement metrics are a poor substitute for quality metrics.
Not a new idea, but they've stepped up the language and announced new signals to encourage sites to stop trying to game the search engine with useless content.
SEO consultants might need to start hiring good writers instead of bean-counters: "We've audited your site and you need 10 more landing pages each containing 250 words of lifeless keyword-stuffed repetition."