Perf seems to be a recurring issue, e.g. see https://gitlab.com/gitlab-com/infrastructure/issues/675

That said, I find the openness with which core architectural issues are discussed to be refreshing. (e.g. see the very detailed writeup explaining the root cause of the above issue, here https://gitlab.com/gitlab-com/infrastructure/issues/677)

Mainly intermittent errors clicking around the interface, particularly 404s when clicking on files that existed - they're not sure whether that was a problem in the web interface or the files actually temporarily went missing.