I love ostree. I have been installing Fedora atomic on everything I own. I have used it so much I have grown to hate it.
They definitely do need a better solution for user management in there. Adding a user to a group on a live system is a pain (because it is poorly documented). I would like to use sysusers to run services but I don't think they can run quadlets. Lots of problems in this area.
They are so close to greatness, though. I sure wish they would get it together.