Some features are missing, but I hope the GitLab team will add sooner or later.
In Jira, there was too much customisation which made it difficult to configure properly and as many times I tried to come up with perfect workflow, I have failed to do.
We have the latter, and it's monster annoying to try and discover in which repo folks filed tickets, because there's nothing in GitLab that validates the ticket belongs in the repo.
Given a magic wand, I would actually just switch off the issue tracker for every repo we have, and create `the-org/issues` or maybe even `the-org/the-org` so I can have `the-org/the-org/wiki` and `the-org/the-org/issues`