From PostgreSQL wiki
We run an ongoing one-question survey on the www.postgresql.org/community page. Typically these are answered by between 200 and 400 users. They are highly unscientific and are interesting rather than terribly informative.
8.4.0 Release Community Survey
Run jointly with EnterpriseDB marketing staff, this was a survey of users that ran for 6 weeks immediately following the version 8.4.0 in July 2009. Most of the respondents were people who downloaded the One-Click Installer. This survey is more complete and informative covering Postgres users, applications, environments, and some commercial considerations. Please note that the audience is limited to early adopters of version 8.4. Also, the questions on the survey pretty much exclude any useful responses from OEMs.
View Online: SurveyMethods
Download files: Media:PostgreSQL_Community_Survey_20090722_Final.zip (includes graphs, XLS and CSV data)
New Community Survey
We need to develop a comprehensive community survey to be run 1-2 months after each new release. This survey should be designed to answer questions more useful to the community. It should probably also run on our infrastructure. Work on this has not been started.