As a very heavy Matrix user, the one thing that's kept me from trying to use it for my local hackerspace is that there's not a simple way to grant access to rooms based on group membership. Within companies/larger private groups, you often (almost always!) want to grant people access to chatrooms conditionally based on membership in the group. There are few options for this right now:

- Have a bot invite everyone in the group to every room and kicks them out if they leave (noisy, not everyone needs to be in every room)

- Have everyone in the group use the same homeserver, make rooms public and non-federated (defeats much of the purpose of Matrix, doesn't let you invite people from outside the org as one-offs)

I think some of the future plans for communities would solve this?

Anyway, Matrix right now is great for both small private chats and FOSS projects; in the former case you can just handle access ad-hoc, and in the latter case the rooms are public anyway. It just seems a bit lacking at the moment for organizations that need private rooms.