http://qwikxxeiw4kgmml6vjw2bsxtviuwjce735dunai2djhu6q7qbacq73id.onion/articles/xmpp/intro
The biggest problem with XMPP is that many of the clients (apps/programs you use to chat with people) could be better.
To some extent, all clients lack features or are buggy or even poorly designed - although, for the most part, it will be
fine.