We spend a lot of time making our Omnibus packages a flawless install and upgrade experience. Docker images are great but for many users Docker is not an option.
GitLab CE is just as performant and easy to upgrade as EE and we strive to keep it that way https://about.gitlab.com/about/#stewardship
Currently our team member Axil is upgrading a GitLab installation from 5.0 all the way to the latest version to ensure it is as smooth as it can be https://twitter.com/gitlab/status/698236575231119360
If you want to know more about upgrading GitLab please see https://about.gitlab.com/update/