The idea seems great, but it's not working: there is no single application that can fit all uses, and you are loosing most of the users on the way.
I'm using Gitlab, btw, but only for the self-hosted git and it's user interface (ie. your core). All the other parts (bug tracking, CI, chat, ...) are in different and more appropriate tools for each of our use-cases... because most of yours are not complete enough, or sometimes it's not even clear how they actually could work for us (mattermost for example).
