I am using Freemius on my giveaway plugin: https://wordpress.org/plugins/giveasap/

For the last 2 weeks of data, people who deactivated it expected it to work differently or do not need it any longer. Other data that I have seen that people do still use WordPress 4.4 and 4.5 so when working on new updates I don't use the latest features such as REST so that everything works ok.

Another thing I have noticed is that people are using PHP 5.5 still and the most used is 5.6.

I am considering getting the Freemius plan upgraded, but for now, until I am fully happy with the plugin's revenue, I'll be still on the free plan. Would love to see the pricing but I guess they are really flexible on that so I will have to contact them directly:)

Great product!