That's the kind of "compelling in theory, irrelevant in practice" comment I would make if I had no/obsolete experience with XMPP. It just works, with a healthy and thriving ecosystem of compatible client/server implementations developed independently by many organisations (small and large) around the world. At the user-level, it's just plug and play. As a developer, you don't even have to see any XML (you can deserialize your stanzas into whatever higher-level/prettier construct the programming language/stack your product depends on)