My own experience is a two years old, but interoperability seemed not to work great. Messages frequently disappeared and all that. As long as you stayed on the

My own experience is a two years old, but interoperability seemed not to work great. Messages frequently disappeared and all that. As long as you stayed on the same instance everything was dandy, but writing to someone one the matrix homeserver worked most of the time. Matrix as a protocol is more exciting than xmpp, but using xmpp (without omemo unless you are all on Conversations) is boring in a good way.