Short version: survey incentivization worked very, veeeeeeerrrry well for increasing response rates. The survey itself got me actionable insights, and when I say that, I mean I did eight commits today based on them. I'd really recommend you try one for your business if you haven't already.
I appreciate that you said you aren't angry at people who complain that your product isn't given for free. I hate it when developers are angry at people who want their software to be free.
Short version: survey incentivization worked very, veeeeeeerrrry well for increasing response rates. The survey itself got me actionable insights, and when I say that, I mean I did eight commits today based on them. I'd really recommend you try one for your business if you haven't already.