There are two main changes here:
Google is removing the "mobile-friendly" label that highlighted pages that were easy to read on mobile from its mobile search results pages
Starting on January 10, 2017, the company will start punishing mobile pages that show intrusive interstitials when a user first opens a page and they will rank lower in its search results.
It should also be noted that "Google won't punish all sites that use interstitials, only the ones that make content less accessible."
In my opinion, it's a move that makes sense, makes UX finally work. I get very frustrated with popups (even though I know they work blah blah) and just end up leaving the website altogether.
What are your thoughts?