If app.net can get the press it has gotten it probably means that the marketplace has reached boiling point. I'm thinking developers and many twitter users are ready for a more reliable and trust-able system.
I'm hopeful to see app.net take off, but have been unable to find any arguments/discussions talking about how app.net will succeed where DIASPORA failed.
(Ignoring the obvious of having a better name, of course!)
Coupled with a lot of negative sentiments that Twitter users and developers feel might make it an interesting story in the tech press. Diaspora had a lot of press when they first started but they couldn't live up to the promise.
In this case it would be easier to live up to the promise because most of the client code already exists. It would largely be a case of clients adding new endpoints to the frontend and abstracting the rendering functions.
It would also be super easy for users to import their Twitter profile into a new system. Just enter a Twitter username and you could easily get the bio & avatar. Very low cost of transfer. If the press pushed it, and it was so easy to move over, it would have a chance IMHO.
I should also point out I don't think app.net has this opportunity, I think it could only happen for a truly free non-profit system.