As an app creator, even in this situation, where the user gets a free ride in your app because she’s a first time App.net user, you’re asking a lot from the user. When user acquisition and retention is your bread and butter, placing a huge level of complexity at the signup step, explaining what the hell an App.net account is, it’s basically strangling the acquisition part, and you never, ever, want to do that.
Taking a step back, what problems are they solving anyway? Shorten time to market for app makers? Because social app plumbing is getting pretty cheap and easy to pull off at scale with IaaS. Besides ending up with something very limited. Using App.net to build your app must add value, either for the creator, or the user. I’m failing to see how it does either. Unless, maybe, if App.net login is an optional part of your app that could lover the already in-place pricing scheme for all users (failing to see when this would make sense, but it’s possibly I guess).
Conclusion: Ask yourself, what app in the past 5 years, could have been pulled off, logistically, using app.net plumbing?