Currently self-hosting my own mastodon server and honestly the setup wasn't too bad (using docker)... much more straight-forward than I feared.

My main concerns, which Julia mentions, is that if you have a small instance, you are very much an island as the way federation work is not what you expect. For instance, as Julia notes, if you view a new person's profile on your own instance, it will look empty (as if they haven't posted anything). Lemmy also has this issue if you view a community you have not subscribed to yet for the first time.

Likewise, my "#explore" tab is basically always empty and discovering new tags or people is difficult if you are just looking on your own instance (I basically have to go to Fossotodon or another instance to find new things and then import them into my own instance). I've recently learned that you have to have a third party application basically seed your instance with posts... again, similar to the bot tricks use for seeding Lemmy with communities.

Overall, I think discovery is a big pain point for the fediverse and ActivityPub. It's great that we can have our own instances and control our own small communities, but it seems that we are lacking the ability to really connect across instances and form experiences that really bridge across multiple communities.