XMPP is more than promising, its proven. The major messaging (and notification, if you believe the rumours) networks are all based on xmpp. The issues are bas

XMPP is more than promising, its proven. The major messaging (and notification, if you believe the rumours) networks are all based on xmpp. The issues are basically: big vendors want lock-in so they disable federation and spam. I remember seeing an XEP that aimed to solve the spam issue for federated xmpp.