I really like XMPP and use it with conversations.im every day. I even have my own XMPP server for friends and family, but it feels as if only very few developers spend time on modern clients. XMPP with its extensions is pretty mature and works great (if properly implemented). Sadly there very few up to date clients. Conversations.im seems to be the exception here. It is very stable, mature and energy efficient, but still lacking audio and video support.

I wish there would be more devs building modern clients for XMPP instead of building the 100th communication system.