An alternative to both downloaded and recommended counts is a simple phone home script implemented as a TTW python script to register as many production sites and what plugins they actually use (and with which version of plone). Then each plugin can have a rating of
"in use by 25% known of plone 5 production sites"
for example.
Basically a slightly better and more automated version of the old Annual Great Backyard Plone Count we used to do. I think a lot of people would be willing to run a simple python script 1-2 a year on each zope install they manage especially if it was opt in and it was simple to filter information they didn't want to reveal (like url and some plugins).
Previously discussed (in Add-on listing for Plone.org) but this is a prototype python script that launches a button that submits plugins on the current site to plone.org where you would then get the option to filter them. I'm pretty sure it will work on any version of plone.
data = context.portal_quickinstaller.listInstalledProducts()
return """<form method="POST" action="http://plone.org/census/@@rapido/plonecensus/block/submit/add">
<textarea name="data">%s</textarea><input type="submit">
</form>""" % data