From a simple user point of view it is easy to cheer for an effort to unify the scattered landscape of free social web services. But it it still a mistery in what direction to cheer to! pump.io will probably support AP, but what about others. What degrees of "support" can be expected? What is the result of putting an AP layer ontop of whatever else you are using? What if it isn't meant to be used as a brige but people end up using it like that? How easy will it be to blame bad user experience (messages get lost, nested replying fails, ...) on bad implementation of AP instead of a flaw of AP?
How realistic is it to hope for interoperability if there isn't even one 100% AP reference implementation?
As a user I'd like to cheer - but given that mess it is hard to see towards what direction. To me this looks more like a fun tool for developers with great ideas, less like the pump.io of tomorrow.