For now basically just that if you use a compatible ejabberd server (community edition support will come a bit later) you will be able to connect to Matrix rooms and contacts with your XMPP client as if those were XMPP contacts.

In the medium term it will probably mean that there is finally a well working and well written Matrix home server as ejabberd is very well tested with literally hundreds of million of users (that doesn’t mean Matrix itself will scale that well though, XMPP is better suited for that).

I think it’s good for users.