Seems like the wordpress.org plugin pages, after recent improvements to the ratings-logic, now got an even more important update. They now use “active installations” as most important metric (as has been done on drupal.org module pages for years), with total number of downloads having been relegated to the stats page.
That stats page got a face-lift as well, featuring a graph of the active versions:
In case you’re wondering what the source of that “active installations” data is, I was too and reached out to plugin-master Otto (Samuel Wood, who replied;
[The source data comes from] plugin update checks. Every WP install asks for update checks every 12 hours or so. We store a count of that info.