I noticed it's used by more and more open source projects and those projects are now publishing exclusively on quay.io
Personally I think this is creating unecessary fragmentation of the docker image repositories.
Also since 3 months there is this warning on quay.io website (all pages): We are currently facing technical issues with support@quay.io email. In order to contact Quay.io customer support, please use the email support@coreos.com until further notice.
Really a tech company not being able to fix an email address for several months is quite concerning.
Why do people consider using Quay.io?