My other big wish for the product is better CI. Gitlab certainly makes Travis unnecessary, but it doesn't scratch the surface of the functionality that Jenkins provides via the plugin ecosystem. Yes Jenkins is janky (although can be made to look nice enough via themes) - but Gitlab doesn't even address parsing xunit results and displaying trends in a project centric reporting location (https://gitlab.com/gitlab-org/gitlab-ce/issues/17081), instead steering you towards build centric "pages". Get the reporting built out (and also allow it to natively consume/parse/understand output from major testing & static analysis frameworks), and it would be a more compelling alternative. Nobody wants to look at hundreds or thousands of lines of build/test output - the CI tool should summarize the reasons for success or failure.
Finally, we're having to run our self-hosted Gitlab on an absurdly large EC2 instance (8 cores, 32GBs). Occasionally we'll have a dozen people converge on a single important PR for review, and before upgrading to our current server this type of event would often bring our instance to its knees. Language choice may be a significant contributor to this -- rewriting major parts of the backend in Go or some JVM language would probably be a good product goal.