Been using GitLab since (I think) 4.0 and have yet to experience any problems upgrading on a fairly standard LAMP-like web server setup on a VPS. To anyone having troubles, what exactly are the errors/problems?

(Late) Edit: any problems I've ever had with upgrades have been related to not properly adjusting settings when moving new config files around. For example, in upgrading to 6.3 I failed to copy over my custom listen lines in unicorn for a non-standard port.